| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/10/28 01:44 | flow | patch-triage |
42mArgs:null Results: {
"EnableConfigs": [
"LIVEUPDATE",
"LIVEUPDATE_MEMFD",
"KEXEC_HANDOVER",
"KEXEC_HANDOVER_ENABLE_DEFAULT",
"MEMFD_CREATE",
"SHMEM",
"TRANSPARENT_HUGEPAGE"
],
"FocusSymbols": [
"memfd_luo_preserve",
"memfd_luo_unpreserve",
"memfd_luo_preserve_folios",
"memfd_luo_migrate_folio",
"shmem_fallocate",
"shmem_setattr",
"shmem_add_to_page_cache",
"shmem_writeout",
"truncate_inode_folio",
"truncate_inode_pages_range",
"folio_unmap_invalidate",
"folio_check_splittable",
"folio_migrate_mapping",
"migrate_huge_page_move_mapping"
],
"KMSANReasoning": "The patch series introduces a generic address_space flag (AS_FROZEN) to prevent modifications to the page cache (folio addition, deletion, migration, splitting, collapsing, truncation) and refactors folio preservation in mm/memfd_luo.c for live updates across kexec.\n\nAnalysis of sanitizers:\n1. KMSAN applicability:\n- The patch does not expose any uninitialized memory to user space via copy_to_user, put_user, netlink, ioctl, or socket interfaces.\n- The structures modified/added (such as struct memfd_luo_folio_ser and struct migration_target_control) are fully initialized before use. The serialization array folios_ser has every element populated sequentially with all fields (pfn, flags, index) set, and all subsequent iterations and cleanup operations strictly bound access to the initialized count (nr_folios).\n- Adding checks for mapping_frozen() simply causes page cache operations (such as write_begin, split, collapse, migrate, remove) to safely fail early with -EBUSY or SCAN_FAIL. No conditional logic branches on uninitialized memory, nor does it allow reading uninitialized bytes from existing buffers.\n\n2. KASAN and other debugging tools:\n- The risks introduced by this patch involve concurrency and synchronization (lock ordering between i_pages xa_lock and inode locks), page cache state invariants, folio migration logic, and folio reference counting (isolating, pinning, and putting folios).\n- These bugs (such as deadlocks, refcounting leaks, use-after-free, or invalid memory accesses) are fully covered by standard KASAN, LOCKDEP, and kernel page asserts (VM_BUG_ON_FOLIO / VM_WARN_ON_ONCE).\n\nTherefore, a dedicated KMSAN fuzzing session is not justified.",
"NeedsKMSAN": false,
"Reasoning": "The patch series introduces a generalized address space frozen state (AS_FROZEN) to disallow modifying folios in frozen mappings, replacing a shmem-specific flag. It enforces this invariant across core memory management, page cache, truncation, migration, THP splitting, khugepaged collapse, and shmem operations. Crucially, it introduces multiple new assertions (WARN_ON_ONCE in evict(), truncate_inode_pages_range(), and shmem_undo_range(), as well as VM_WARN_ON_ONCE checks in filemap.c) to enforce mapping invariants. Furthermore, it completely refactors folio preservation and folio migration in mm/memfd_luo.c. Because these modifications impact core MM/VFS subsystems and add new invariants reachable via memfd operations and the liveupdate ioctl interface, fuzzing is strongly warranted.",
"WorthFuzzing": true
} |
| 1/1 | 2026/10/28 01:44 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit d3dd9b6fca9a06703893cd89e47456874917efa8\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Oct 28 01:44:06 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/fs/inode.c b/fs/inode.c\nindex a9d37be390a173..635083c42419fc 100644\n--- a/fs/inode.c\n+++ b/fs/inode.c\n@@ -7,6 +7,7 @@\n #include \u003clinux/fs.h\u003e\n #include \u003clinux/filelock.h\u003e\n #include \u003clinux/mm.h\u003e\n+#include \u003clinux/pagemap.h\u003e\n #include \u003clinux/backing-dev.h\u003e\n #include \u003clinux/hash.h\u003e\n #include \u003clinux/swap.h\u003e\n@@ -818,6 +819,14 @@ static void evict(struct inode *inode)\n \tinode_wait_for_writeback(inode);\n \tspin_unlock(\u0026inode-\u003ei_lock);\n \n+\t/*\n+\t * Whoever froze the mapping must hold an inode reference until it is\n+\t * unfrozen, so this should never happen. If it does, unfreeze it so\n+\t * the final truncate does not leak folios.\n+\t */\n+\tif (WARN_ON_ONCE(mapping_frozen(\u0026inode-\u003ei_data)))\n+\t\tclear_bit(AS_FROZEN, \u0026inode-\u003ei_data.flags);\n+\n \tif (op-\u003eevict_inode) {\n \t\top-\u003eevict_inode(inode);\n \t} else {\ndiff --git a/include/linux/pagemap.h b/include/linux/pagemap.h\nindex 73af18a3736706..9b9d0459f39922 100644\n--- a/include/linux/pagemap.h\n+++ b/include/linux/pagemap.h\n@@ -209,6 +209,7 @@ enum mapping_flags {\n \tAS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,\n \tAS_KERNEL_FILE = 10,\t/* mapping for a fake kernel file that shouldn't\n \t\t\t\t account usage to user cgroups */\n+\tAS_FROZEN = 11,\t\t/* index -\u003e folio mapping must not change */\n \t/* Bits 16-25 are used for FOLIO_ORDER */\n \tAS_FOLIO_ORDER_BITS = 5,\n \tAS_FOLIO_ORDER_MIN = 16,\n@@ -344,6 +345,40 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres\n \treturn test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, \u0026mapping-\u003eflags);\n }\n \n+/*\n+ * A frozen mapping disallows any change to its i_pages: no folio can be added,\n+ * removed, replaced (migration, swap out), split, or collapsed.\n+ *\n+ * Only the page cache is frozen, not the file. Operations that need to change\n+ * the page cache fail with -EBUSY, e.g. a write or fault that needs to allocate\n+ * a new folio. Others, like reading or writing (to pages already in i_pages),\n+ * still work.\n+ *\n+ * Locking: the flag is flipped under the i_pages lock. The filesystem must\n+ * ensure mapping_set_frozen() doesn't race with a truncate or fallocate, since\n+ * those can fail if frozen mid-way.\n+ *\n+ * The mapping must be unfrozen before the inode is evicted.\n+ */\n+static inline void mapping_set_frozen(struct address_space *mapping)\n+{\n+\txa_lock_irq(\u0026mapping-\u003ei_pages);\n+\tset_bit(AS_FROZEN, \u0026mapping-\u003eflags);\n+\txa_unlock_irq(\u0026mapping-\u003ei_pages);\n+}\n+\n+static inline void mapping_clear_frozen(struct address_space *mapping)\n+{\n+\txa_lock_irq(\u0026mapping-\u003ei_pages);\n+\tclear_bit(AS_FROZEN, \u0026mapping-\u003eflags);\n+\txa_unlock_irq(\u0026mapping-\u003ei_pages);\n+}\n+\n+static inline bool mapping_frozen(const struct address_space *mapping)\n+{\n+\treturn test_bit(AS_FROZEN, \u0026mapping-\u003eflags);\n+}\n+\n static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)\n {\n \treturn mapping-\u003egfp_mask;\ndiff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h\nindex a7c7a96a7cbf90..5b48598a7b9523 100644\n--- a/include/linux/shmem_fs.h\n+++ b/include/linux/shmem_fs.h\n@@ -23,14 +23,6 @@\n #define SHMEM_F_NORESERVE\tBIT(0)\n /* Disallow swapping. */\n #define SHMEM_F_LOCKED\t\tBIT(1)\n-/*\n- * Disallow growing, shrinking, or hole punching in the inode. Combined with\n- * folio pinning, makes sure the inode's mapping stays fixed.\n- *\n- * In some ways similar to F_SEAL_GROW | F_SEAL_SHRINK, but can be removed and\n- * isn't directly visible to userspace.\n- */\n-#define SHMEM_F_MAPPING_FROZEN\tBIT(2)\n \n struct shmem_inode_info {\n \tspinlock_t\t\tlock;\n@@ -202,15 +194,6 @@ static inline bool shmem_file(struct file *file)\n \treturn shmem_mapping(file-\u003ef_mapping);\n }\n \n-/* Must be called with inode lock taken exclusive. */\n-static inline void shmem_freeze(struct inode *inode, bool freeze)\n-{\n-\tif (freeze)\n-\t\tSHMEM_I(inode)-\u003eflags |= SHMEM_F_MAPPING_FROZEN;\n-\telse\n-\t\tSHMEM_I(inode)-\u003eflags \u0026= ~SHMEM_F_MAPPING_FROZEN;\n-}\n-\n /*\n * If fallocate(FALLOC_FL_KEEP_SIZE) has been used, there may be pages\n * beyond i_size's notion of EOF, which fallocate has committed to reserving:\ndiff --git a/mm/filemap.c b/mm/filemap.c\nindex b74bc1e5015c6f..d040c69177f792 100644\n--- a/mm/filemap.c\n+++ b/mm/filemap.c\n@@ -138,6 +138,7 @@ static void page_cache_delete(struct address_space *mapping,\n \tnr = folio_nr_pages(folio);\n \n \tVM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);\n+\tVM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), folio);\n \n \txas_store(\u0026xas, shadow);\n \txas_init_marks(\u0026xas);\n@@ -284,6 +285,7 @@ static void page_cache_delete_batch(struct address_space *mapping,\n \tint i = 0;\n \tstruct folio *folio;\n \n+\tVM_WARN_ON_ONCE(mapping_frozen(mapping));\n \tmapping_set_update(\u0026xas, mapping);\n \txas_for_each(\u0026xas, folio, ULONG_MAX) {\n \t\tif (i \u003e= folio_batch_count(fbatch))\n@@ -826,6 +828,7 @@ void replace_page_cache_folio(struct folio *old, struct folio *new)\n \tmem_cgroup_replace_folio(old, new);\n \n \txas_lock_irq(\u0026xas);\n+\tVM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), old);\n \txas_store(\u0026xas, new);\n \n \told-\u003emapping = NULL;\n@@ -873,6 +876,10 @@ noinline int __filemap_add_folio(struct address_space *mapping,\n \t\tvoid *entry, *old = NULL;\n \n \t\txas_lock_irq(\u0026xas);\n+\t\tif (unlikely(mapping_frozen(mapping))) {\n+\t\t\txas_set_err(\u0026xas, -EBUSY);\n+\t\t\tgoto unlock;\n+\t\t}\n \t\txas_for_each_conflict(\u0026xas, entry) {\n \t\t\told = entry;\n \t\t\tif (!xa_is_value(entry)) {\ndiff --git a/mm/huge_memory.c b/mm/huge_memory.c\nindex bd44d58e86845c..06d2f71ec74981 100644\n--- a/mm/huge_memory.c\n+++ b/mm/huge_memory.c\n@@ -3948,6 +3948,10 @@ int folio_check_splittable(struct folio *folio, unsigned int new_order,\n \tif (!folio-\u003emapping \u0026\u0026 !is_anon)\n \t\treturn -EBUSY;\n \n+\t/* Splitting would change a frozen mapping. */\n+\tif (!folio_test_anon(folio) \u0026\u0026 mapping_frozen(folio-\u003emapping))\n+\t\treturn -EBUSY;\n+\n \t/* order-1 is not supported for anonymous THP. */\n \tif (is_anon \u0026\u0026 new_order == 1)\n \t\treturn -EINVAL;\n@@ -4186,6 +4190,12 @@ static int __folio_freeze_split_file(struct folio *folio,\n \n \txas_lock_irq(\u0026xas);\n \n+\t/* Can't change a frozen mapping. */\n+\tif (mapping_frozen(mapping)) {\n+\t\tret = -EBUSY;\n+\t\tgoto fail;\n+\t}\n+\n \t/*\n \t * Check if the folio is present in page cache.\n \t * We assume all tail are present too, if folio is there.\ndiff --git a/mm/khugepaged.c b/mm/khugepaged.c\nindex da91762f6358f2..5c78573f57c473 100644\n--- a/mm/khugepaged.c\n+++ b/mm/khugepaged.c\n@@ -2531,6 +2531,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\n \t\ti_mmap_lock_read(mapping);\n \t\txas_lock_irq(\u0026xas);\n \n+\t\t/* Can't collapse folios in a frozen mapping. */\n+\t\tif (mapping_frozen(mapping)) {\n+\t\t\tresult = SCAN_FAIL;\n+\t\t\tgoto immap_locked;\n+\t\t}\n+\n \t\txas_set(\u0026xas, start);\n \t\tfor (index = start; index \u003c end; index++) {\n \t\t\tif (!xas_next(\u0026xas)) {\n@@ -2582,6 +2588,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\n \t\t}\n \t} else {\n \t\txas_lock_irq(\u0026xas);\n+\t\t/* Can't collapse folios in a frozen mapping. */\n+\t\tif (mapping_frozen(mapping)) {\n+\t\t\txas_unlock_irq(\u0026xas);\n+\t\t\tresult = SCAN_FAIL;\n+\t\t\tgoto rollback;\n+\t\t}\n \t}\n \n \tif (is_shmem) {\ndiff --git a/mm/memfd_luo.c b/mm/memfd_luo.c\nindex 59de210bee5f9e..ec5abd41ecb8ba 100644\n--- a/mm/memfd_luo.c\n+++ b/mm/memfd_luo.c\n@@ -77,26 +77,127 @@\n #include \u003clinux/kexec_handover.h\u003e\n #include \u003clinux/kho/abi/memfd.h\u003e\n #include \u003clinux/liveupdate.h\u003e\n+#include \u003clinux/migrate.h\u003e\n+#include \u003clinux/sched/mm.h\u003e\n+#include \u003clinux/sched/signal.h\u003e\n #include \u003clinux/shmem_fs.h\u003e\n+#include \u003clinux/swap.h\u003e\n #include \u003clinux/vmalloc.h\u003e\n #include \u003clinux/memfd.h\u003e\n+#include \u003clinux/pagemap.h\u003e\n #include \u003cuapi/linux/memfd.h\u003e\n \n #include \"internal.h\"\n \n+static void memfd_luo_put_folios(const struct memfd_luo_folio_ser *folios_ser,\n+\t\t\t\t u64 nr_folios)\n+{\n+\tu64 i;\n+\n+\tfor (i = 0; i \u003c nr_folios; i++) {\n+\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\n+\t\tstruct folio *folio;\n+\n+\t\tif (!pfolio-\u003epfn)\n+\t\t\tcontinue;\n+\n+\t\tfolio = pfn_folio(pfolio-\u003epfn);\n+\n+\t\tkho_unpreserve_folio(folio);\n+\t\tfolio_put(folio);\n+\t}\n+}\n+\n+/* How many times to retry isolating a folio someone else has isolated. */\n+#define MEMFD_LUO_MIGRATE_RETRIES\t3\n+\n+/*\n+ * Move a folio out of ZONE_MOVABLE or CMA, so it can be held until the next\n+ * kernel. Called with a reference on the unlocked folio, which is always\n+ * dropped. The caller must look up the folio again afterwards.\n+ *\n+ * Returns 0 on success, -EBUSY if the folio could not be isolated (e.g.\n+ * because someone else has it isolated right now), or -ENOMEM if migration\n+ * failed.\n+ */\n+static int memfd_luo_migrate_folio(struct folio *folio)\n+{\n+\tstruct migration_target_control mtc = {\n+\t\t.nid = NUMA_NO_NODE,\n+\t\t/* Not movable, so the target is neither in ZONE_MOVABLE nor CMA. */\n+\t\t.gfp_mask = GFP_USER | __GFP_NOWARN,\n+\t\t.reason = MR_LONGTERM_PIN,\n+\t};\n+\tLIST_HEAD(source);\n+\tbool isolated;\n+\n+\t/* Flush per-CPU LRU batches holding the folio so isolation works. */\n+\tlru_cache_drain_for_folio(folio, 1, NULL);\n+\tisolated = isolate_folio_to_list(folio, \u0026source);\n+\t/* Isolation holds its own reference. */\n+\tfolio_put(folio);\n+\tif (!isolated)\n+\t\treturn -EBUSY;\n+\n+\tif (migrate_pages(\u0026source, alloc_migration_target, NULL,\n+\t\t\t (unsigned long)\u0026mtc, MIGRATE_SYNC, MR_LONGTERM_PIN,\n+\t\t\t NULL)) {\n+\t\tputback_movable_pages(\u0026source);\n+\t\treturn -ENOMEM;\n+\t}\n+\n+\treturn 0;\n+}\n+\n+static int memfd_luo_preserve_folio(struct folio *folio,\n+\t\t\t\t struct memfd_luo_folio_ser *pfolio)\n+{\n+\tint err;\n+\n+\terr = kho_preserve_folio(folio);\n+\tif (err)\n+\t\treturn err;\n+\n+\t/*\n+\t * A dirty folio is one which has been written to. A clean folio\n+\t * is its opposite. Since a clean folio does not carry user\n+\t * data, it can be freed by page reclaim under memory pressure.\n+\t *\n+\t * Saving the dirty flag at prepare() time doesn't work since it\n+\t * can change later. Saving it at freeze() also won't work\n+\t * because the dirty bit is normally synced at unmap and there\n+\t * might still be a mapping of the file at freeze().\n+\t *\n+\t * To see why this is a problem, say a folio is clean at\n+\t * preserve, but gets dirtied later. The pfolio flags will mark\n+\t * it as clean. After retrieve, the next kernel might try to\n+\t * reclaim this folio under memory pressure, losing user data.\n+\t *\n+\t * Unconditionally mark it dirty to avoid this problem. This\n+\t * comes at the cost of making clean folios un-reclaimable after\n+\t * live update.\n+\t */\n+\tfolio_mark_dirty(folio);\n+\n+\tpfolio-\u003epfn = folio_pfn(folio);\n+\tpfolio-\u003eflags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;\n+\tpfolio-\u003eindex = folio-\u003eindex;\n+\n+\treturn 0;\n+}\n+\n static int memfd_luo_preserve_folios(struct file *file,\n \t\t\t\t struct kho_vmalloc *kho_vmalloc,\n \t\t\t\t struct memfd_luo_folio_ser **out_folios_ser,\n \t\t\t\t u64 *nr_foliosp)\n {\n+\tstruct memfd_luo_folio_ser *folios_ser, *shrunk;\n \tstruct inode *inode = file_inode(file);\n-\tstruct memfd_luo_folio_ser *folios_ser;\n-\tunsigned int max_folios;\n-\tlong i, size, nr_pinned;\n-\tstruct folio **folios;\n-\tint err = -EINVAL;\n-\tpgoff_t offset;\n-\tu64 nr_folios;\n+\tu64 nr_folios = 0, max_folios;\n+\tint err, busy_retries = 0;\n+\tunsigned int pin_flags;\n+\tpgoff_t index = 0, end;\n+\tloff_t size;\n \n \tsize = i_size_read(inode);\n \t/*\n@@ -113,99 +214,77 @@ static int memfd_luo_preserve_folios(struct file *file,\n \t * Guess the number of folios based on inode size. Real number might end\n \t * up being smaller if there are higher order folios.\n \t */\n-\tmax_folios = PAGE_ALIGN(size) / PAGE_SIZE;\n-\tfolios = kvmalloc_objs(*folios, max_folios);\n-\tif (!folios)\n+\tend = DIV_ROUND_UP_ULL(size, PAGE_SIZE);\n+\tmax_folios = end;\n+\tfolios_ser = vmalloc_array(max_folios, sizeof(*folios_ser));\n+\tif (!folios_ser)\n \t\treturn -ENOMEM;\n \n \t/*\n-\t * Pin the folios so they don't move around behind our back. This also\n-\t * ensures none of the folios are in CMA -- which ensures they don't\n-\t * fall in KHO scratch memory. It also moves swapped out folios back to\n-\t * memory.\n+\t * The folios are held until the next kernel, so keep newly allocated\n+\t * ones out of ZONE_MOVABLE and CMA -- which also ensures they don't\n+\t * fall in KHO bootmem. Existing ones are migrated below.\n \t *\n-\t * A side effect of doing this is that it allocates a folio for all\n-\t * indices in the file. This might waste memory on sparse memfds. If\n-\t * that is really a problem in the future, we can have a\n-\t * memfd_pin_folios() variant that does not allocate a page on empty\n-\t * slots.\n+\t * A side effect of this is that it allocates a folio for all indices in\n+\t * the file. This might waste memory on sparse memfds. If that is really\n+\t * a problem in the future, this loop can be taught to skip empty slots.\n \t */\n-\tnr_pinned = memfd_pin_folios(file, 0, size - 1, folios, max_folios,\n-\t\t\t\t \u0026offset);\n-\tif (nr_pinned \u003c 0) {\n-\t\terr = nr_pinned;\n-\t\tpr_err(\"failed to pin folios: %d\\n\", err);\n-\t\tgoto err_free_folios;\n-\t}\n-\tnr_folios = nr_pinned;\n+\tpin_flags = memalloc_pin_save();\n+\twhile (index \u003c end) {\n+\t\tstruct folio *folio;\n \n-\tfolios_ser = vcalloc(nr_folios, sizeof(*folios_ser));\n-\tif (!folios_ser) {\n-\t\terr = -ENOMEM;\n-\t\tgoto err_unpin;\n-\t}\n+\t\tcond_resched();\n \n-\tfor (i = 0; i \u003c nr_folios; i++) {\n-\t\tstruct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\n-\t\tstruct folio *folio = folios[i];\n+\t\tif (fatal_signal_pending(current)) {\n+\t\t\terr = -EINTR;\n+\t\t\tgoto err_restore;\n+\t\t}\n+\n+\t\tif (WARN_ON_ONCE(nr_folios \u003e= max_folios)) {\n+\t\t\terr = -EINVAL;\n+\t\t\tgoto err_restore;\n+\t\t}\n \n-\t\terr = kho_preserve_folio(folio);\n+\t\terr = shmem_get_folio(inode, index, 0, \u0026folio, SGP_CACHE);\n \t\tif (err)\n-\t\t\tgoto err_unpreserve;\n-\n-\t\tfolio_lock(folio);\n-\n-\t\t/*\n-\t\t * A dirty folio is one which has been written to. A clean folio\n-\t\t * is its opposite. Since a clean folio does not carry user\n-\t\t * data, it can be freed by page reclaim under memory pressure.\n-\t\t *\n-\t\t * Saving the dirty flag at prepare() time doesn't work since it\n-\t\t * can change later. Saving it at freeze() also won't work\n-\t\t * because the dirty bit is normally synced at unmap and there\n-\t\t * might still be a mapping of the file at freeze().\n-\t\t *\n-\t\t * To see why this is a problem, say a folio is clean at\n-\t\t * preserve, but gets dirtied later. The pfolio flags will mark\n-\t\t * it as clean. After retrieve, the next kernel might try to\n-\t\t * reclaim this folio under memory pressure, losing user data.\n-\t\t *\n-\t\t * Unconditionally mark it dirty to avoid this problem. This\n-\t\t * comes at the cost of making clean folios un-reclaimable after\n-\t\t * live update.\n-\t\t */\n-\t\tfolio_mark_dirty(folio);\n-\n-\t\t/*\n-\t\t * If the folio is not uptodate, it was fallocated but never\n-\t\t * used. Saving this flag at prepare() doesn't work since it\n-\t\t * might change later when someone uses the folio.\n-\t\t *\n-\t\t * Since we have taken the performance penalty of allocating,\n-\t\t * zeroing, and pinning all the folios in the holes, take a bit\n-\t\t * more and zero all non-uptodate folios too.\n-\t\t *\n-\t\t * NOTE: For someone looking to improve preserve performance,\n-\t\t * this is a good place to look.\n-\t\t */\n-\t\tif (!folio_test_uptodate(folio)) {\n-\t\t\tfolio_zero_range(folio, 0, folio_size(folio));\n-\t\t\tflush_dcache_folio(folio);\n-\t\t\tfolio_mark_uptodate(folio);\n+\t\t\tgoto err_restore;\n+\n+\t\tif (unlikely(!folio_is_longterm_pinnable(folio))) {\n+\t\t\tfolio_unlock(folio);\n+\t\t\terr = memfd_luo_migrate_folio(folio);\n+\t\t\t/* Someone else might have it isolated, retry a bit. */\n+\t\t\tif (err == -EBUSY \u0026\u0026 ++busy_retries \u003c MEMFD_LUO_MIGRATE_RETRIES)\n+\t\t\t\tcontinue;\n+\t\t\tif (err)\n+\t\t\t\tgoto err_restore;\n+\t\t\tcontinue;\n \t\t}\n \n+\t\terr = memfd_luo_preserve_folio(folio, \u0026folios_ser[nr_folios]);\n+\t\tindex = folio_next_index(folio);\n \t\tfolio_unlock(folio);\n-\n-\t\tpfolio-\u003epfn = folio_pfn(folio);\n-\t\tpfolio-\u003eflags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;\n-\t\tpfolio-\u003eindex = folio-\u003eindex;\n+\t\tif (err) {\n+\t\t\tfolio_put(folio);\n+\t\t\tgoto err_restore;\n+\t\t}\n+\t\tnr_folios++;\n+\t\tbusy_retries = 0;\n \t}\n+\tmemalloc_pin_restore(pin_flags);\n+\n+\t/*\n+\t * Free the unused tail so it doesn't get preserved. If vrealloc fails,\n+\t * the folios_ser is still valid.\n+\t */\n+\tshrunk = vrealloc(folios_ser, array_size(nr_folios, sizeof(*folios_ser)),\n+\t\t\t GFP_KERNEL);\n+\tif (shrunk)\n+\t\tfolios_ser = shrunk;\n \n \terr = kho_preserve_vmalloc(folios_ser, kho_vmalloc);\n \tif (err)\n-\t\tgoto err_unpreserve;\n+\t\tgoto err_put;\n \n-\tkvfree(folios);\n \t*nr_foliosp = nr_folios;\n \t*out_folios_ser = folios_ser;\n \n@@ -216,15 +295,11 @@ static int memfd_luo_preserve_folios(struct file *file,\n \t */\n \treturn 0;\n \n-err_unpreserve:\n-\tfor (i = i - 1; i \u003e= 0; i--)\n-\t\tkho_unpreserve_folio(folios[i]);\n+err_restore:\n+\tmemalloc_pin_restore(pin_flags);\n+err_put:\n+\tmemfd_luo_put_folios(folios_ser, nr_folios);\n \tvfree(folios_ser);\n-err_unpin:\n-\tunpin_folios(folios, nr_folios);\n-err_free_folios:\n-\tkvfree(folios);\n-\n \treturn err;\n }\n \n@@ -232,26 +307,11 @@ static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,\n \t\t\t\t\tstruct memfd_luo_folio_ser *folios_ser,\n \t\t\t\t\tu64 nr_folios)\n {\n-\tlong i;\n-\n \tif (!nr_folios)\n \t\treturn;\n \n \tkho_unpreserve_vmalloc(kho_vmalloc);\n-\n-\tfor (i = 0; i \u003c nr_folios; i++) {\n-\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\n-\t\tstruct folio *folio;\n-\n-\t\tif (!pfolio-\u003epfn)\n-\t\t\tcontinue;\n-\n-\t\tfolio = pfn_folio(pfolio-\u003epfn);\n-\n-\t\tkho_unpreserve_folio(folio);\n-\t\tunpin_folio(folio);\n-\t}\n-\n+\tmemfd_luo_put_folios(folios_ser, nr_folios);\n \tvfree(folios_ser);\n }\n \n@@ -264,7 +324,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\n \tint err = 0, seals;\n \n \tinode_lock(inode);\n-\tshmem_freeze(inode, true);\n \n \t/* Allocate the main serialization structure in preserved memory */\n \tser = kho_alloc_preserve(sizeof(*ser));\n@@ -288,15 +347,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\n \tser-\u003epos = args-\u003efile-\u003ef_pos;\n \tinode_size = i_size_read(inode);\n \n-\t/*\n-\t * memfd_pin_folios() caps at UINT_MAX folios; refuse larger\n-\t * files to avoid silently preserving only a prefix.\n-\t */\n-\tif (DIV_ROUND_UP_ULL(inode_size, PAGE_SIZE) \u003e UINT_MAX) {\n-\t\terr = -EFBIG;\n-\t\tgoto err_free_ser;\n-\t}\n-\n \tser-\u003esize = inode_size;\n \tser-\u003eseals = seals;\n \n@@ -305,6 +355,12 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\n \tif (err)\n \t\tgoto err_free_ser;\n \n+\t/*\n+\t * All the folios in the file are now stable. Freeze the mapping to make\n+\t * sure new ones can't be added.\n+\t */\n+\tmapping_set_frozen(inode-\u003ei_mapping);\n+\n \tser-\u003enr_folios = nr_folios;\n \tinode_unlock(inode);\n \n@@ -316,7 +372,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\n err_free_ser:\n \tkho_unpreserve_free(ser);\n err_unlock:\n-\tshmem_freeze(inode, false);\n \tinode_unlock(inode);\n \treturn err;\n }\n@@ -348,7 +403,7 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)\n \t\treturn;\n \n \tinode_lock(inode);\n-\tshmem_freeze(inode, false);\n+\tmapping_clear_frozen(inode-\u003ei_mapping);\n \n \tser = phys_to_virt(args-\u003eserialized_data);\n \ndiff --git a/mm/migrate.c b/mm/migrate.c\nindex d649a6cfce6c09..6ce01871d72e39 100644\n--- a/mm/migrate.c\n+++ b/mm/migrate.c\n@@ -614,10 +614,16 @@ static int __folio_migrate_mapping(struct address_space *mapping,\n \toldzone = folio_zone(folio);\n \tnewzone = folio_zone(newfolio);\n \n-\tif (folio_test_swapcache(folio))\n+\tif (folio_test_swapcache(folio)) {\n \t\tci = swap_cluster_get_and_lock_irq(folio);\n-\telse\n+\t} else {\n \t\txas_lock_irq(\u0026xas);\n+\t\t/* Can't replace folios in a frozen mapping. */\n+\t\tif (mapping_frozen(mapping)) {\n+\t\t\txas_unlock_irq(\u0026xas);\n+\t\t\treturn -EBUSY;\n+\t\t}\n+\t}\n \n \tif (!folio_ref_freeze(folio, expected_count)) {\n \t\tif (ci)\n@@ -750,6 +756,10 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,\n \t\treturn rc;\n \n \txas_lock_irq(\u0026xas);\n+\tif (mapping_frozen(mapping)) {\n+\t\txas_unlock_irq(\u0026xas);\n+\t\treturn -EBUSY;\n+\t}\n \tif (!folio_ref_freeze(src, expected_count)) {\n \t\txas_unlock_irq(\u0026xas);\n \t\treturn -EAGAIN;\ndiff --git a/mm/shmem.c b/mm/shmem.c\nindex 13e0786436cda1..1c70fd306bec21 100644\n--- a/mm/shmem.c\n+++ b/mm/shmem.c\n@@ -1121,6 +1121,10 @@ int shmem_add_to_page_cache(struct folio *folio,\n \tdo {\n \t\titer = swap;\n \t\txas_lock_irq(\u0026xas);\n+\t\tif (unlikely(mapping_frozen(mapping))) {\n+\t\t\txas_set_err(\u0026xas, -EBUSY);\n+\t\t\tgoto unlock;\n+\t\t}\n \t\txas_for_each_conflict(\u0026xas, entry) {\n \t\t\t/*\n \t\t\t * The range must either be empty, or filled with\n@@ -1345,6 +1349,10 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,\n \tif (lend == -1)\n \t\tend = -1;\t/* unsigned, so actually very big */\n \n+\t/* Callers must not try to truncate a frozen mapping. */\n+\tif (WARN_ON_ONCE(mapping_frozen(mapping)))\n+\t\treturn;\n+\n \tif (info-\u003efallocend \u003e start \u0026\u0026 info-\u003efallocend \u003c= end \u0026\u0026 !unfalloc)\n \t\tinfo-\u003efallocend = start;\n \n@@ -1562,8 +1570,6 @@ static int shmem_setattr(struct mnt_idmap *idmap,\n \t\t\treturn -EPERM;\n \n \t\tif (newsize != oldsize) {\n-\t\t\tif (info-\u003eflags \u0026 SHMEM_F_MAPPING_FROZEN)\n-\t\t\t\treturn -EPERM;\n \t\t\terror = shmem_reacct_size(SHMEM_I(inode)-\u003eflags,\n \t\t\t\t\toldsize, newsize);\n \t\t\tif (error)\n@@ -1575,6 +1581,11 @@ static int shmem_setattr(struct mnt_idmap *idmap,\n \t\t}\n \t\tif (newsize \u003c= oldsize) {\n \t\t\tloff_t holebegin = round_up(newsize, PAGE_SIZE);\n+\n+\t\t\t/* No truncation allowed on a frozen mapping. */\n+\t\t\tif (mapping_frozen(inode-\u003ei_mapping))\n+\t\t\t\treturn -EBUSY;\n+\n \t\t\tif (oldsize \u003e holebegin)\n \t\t\t\tunmap_mapping_range(inode-\u003ei_mapping,\n \t\t\t\t\t\t\tholebegin, 0, 1);\n@@ -1822,6 +1833,10 @@ int shmem_writeout(struct swap_io_ctx *ctx, struct folio *folio,\n \tif ((info-\u003eflags \u0026 SHMEM_F_LOCKED) || sbinfo-\u003enoswap)\n \t\tgoto redirty;\n \n+\t/* Swapping out would replace the folio in a frozen mapping. */\n+\tif (mapping_frozen(mapping))\n+\t\tgoto redirty;\n+\n \tif (!total_swap_pages)\n \t\tgoto redirty;\n \n@@ -2483,6 +2498,13 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,\n \tif (softleaf_is_poison_marker(index_entry))\n \t\treturn -EIO;\n \n+\t/*\n+\t * Swapping in would change the i_pages of a frozen mapping. A frozen\n+\t * mapping should not have swap entries in the first place.\n+\t */\n+\tif (unlikely(mapping_frozen(mapping)))\n+\t\treturn -EBUSY;\n+\n \tsi = get_swap_device(index_entry);\n \torder = shmem_confirm_swap(mapping, index, index_entry);\n \tif (IS_ERR_OR_NULL(si)) {\n@@ -3463,10 +3485,6 @@ shmem_write_begin(const struct kiocb *iocb, struct address_space *mapping,\n \t\t\treturn -EPERM;\n \t}\n \n-\tif (unlikely((info-\u003eflags \u0026 SHMEM_F_MAPPING_FROZEN) \u0026\u0026\n-\t\t pos + len \u003e inode-\u003ei_size))\n-\t\treturn -EPERM;\n-\n \tret = shmem_get_folio(inode, index, pos + len, \u0026folio, SGP_WRITE);\n \tif (ret)\n \t\treturn ret;\n@@ -3841,8 +3859,8 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,\n \n \tinode_lock(inode);\n \n-\tif (info-\u003eflags \u0026 SHMEM_F_MAPPING_FROZEN) {\n-\t\terror = -EPERM;\n+\tif (mapping_frozen(inode-\u003ei_mapping)) {\n+\t\terror = -EBUSY;\n \t\tgoto out;\n \t}\n \ndiff --git a/mm/truncate.c b/mm/truncate.c\nindex 733d2713a875a5..6512f460a28e94 100644\n--- a/mm/truncate.c\n+++ b/mm/truncate.c\n@@ -171,6 +171,8 @@ int truncate_inode_folio(struct address_space *mapping, struct folio *folio)\n {\n \tif (folio-\u003emapping != mapping)\n \t\treturn -EIO;\n+\tif (mapping_frozen(mapping))\n+\t\treturn -EBUSY;\n \n \ttruncate_cleanup_folio(folio);\n \tfilemap_remove_folio(folio);\n@@ -367,6 +369,8 @@ long mapping_evict_folio(struct address_space *mapping, struct folio *folio)\n \t\treturn 0;\n \tif (folio_test_dirty(folio) || folio_test_writeback(folio))\n \t\treturn 0;\n+\tif (mapping_frozen(mapping))\n+\t\treturn 0;\n \t/* The refcount will be elevated if any page in the folio is mapped */\n \tif (folio_ref_count(folio) \u003e\n \t\t\tfolio_nr_pages(folio) + folio_has_private(folio) + 1)\n@@ -419,6 +423,13 @@ void truncate_inode_pages_range(struct address_space *mapping,\n \tif (mapping_empty(mapping))\n \t\treturn;\n \n+\t/*\n+\t * Callers must not try to truncate a frozen mapping. Filesystems that\n+\t * support frozen mappings must refuse shrinking and hole punching\n+\t * before getting here.\n+\t */\n+\tif (WARN_ON_ONCE(mapping_frozen(mapping)))\n+\t\treturn;\n \t/*\n \t * 'start' and 'end' always covers the range of folios to be fully\n \t * truncated, with both boundaries aligned inwards to 1 \u003c\u003c min_order.\n@@ -668,6 +679,9 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,\n \n \tVM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);\n \n+\tif (mapping_frozen(mapping))\n+\t\treturn -EBUSY;\n+\n \tif (folio_mapped(folio))\n \t\tunmap_mapping_folio(folio);\n \tBUG_ON(folio_mapped(folio));\n@@ -682,7 +696,7 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,\n \n \tspin_lock(\u0026mapping-\u003ehost-\u003ei_lock);\n \txa_lock_irq(\u0026mapping-\u003ei_pages);\n-\tif (folio_test_dirty(folio))\n+\tif (folio_test_dirty(folio) || mapping_frozen(mapping))\n \t\tgoto failed;\n \n \tBUG_ON(folio_has_private(folio));\ndiff --git a/mm/vmscan.c b/mm/vmscan.c\nindex 9959ca158ce835..86ef233e8752ee 100644\n--- a/mm/vmscan.c\n+++ b/mm/vmscan.c\n@@ -766,6 +766,9 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,\n \t} else {\n \t\tspin_lock(\u0026mapping-\u003ehost-\u003ei_lock);\n \t\txa_lock_irq(\u0026mapping-\u003ei_pages);\n+\t\t/* Can't remove folios from a frozen mapping. */\n+\t\tif (mapping_frozen(mapping))\n+\t\t\tgoto cannot_free;\n \t}\n \n \t/*\n"
} |
| 2/1 | 2026/10/28 01:44 | agent | patch-evaluator |
13mModel:core Args: null Results: {
"EnableConfigs": [
"LIVEUPDATE",
"LIVEUPDATE_MEMFD",
"KEXEC_HANDOVER",
"KEXEC_HANDOVER_ENABLE_DEFAULT",
"MEMFD_CREATE",
"SHMEM",
"TRANSPARENT_HUGEPAGE"
],
"FocusSymbols": [
"memfd_luo_preserve",
"memfd_luo_unpreserve",
"memfd_luo_preserve_folios",
"memfd_luo_migrate_folio",
"shmem_fallocate",
"shmem_setattr",
"shmem_add_to_page_cache",
"shmem_writeout",
"truncate_inode_folio",
"truncate_inode_pages_range",
"folio_unmap_invalidate",
"folio_check_splittable",
"folio_migrate_mapping",
"migrate_huge_page_move_mapping"
],
"Reasoning": "The patch series introduces a generalized address space frozen state (AS_FROZEN) to disallow modifying folios in frozen mappings, replacing a shmem-specific flag. It enforces this invariant across core memory management, page cache, truncation, migration, THP splitting, khugepaged collapse, and shmem operations. Crucially, it introduces multiple new assertions (WARN_ON_ONCE in evict(), truncate_inode_pages_range(), and shmem_undo_range(), as well as VM_WARN_ON_ONCE checks in filemap.c) to enforce mapping invariants. Furthermore, it completely refactors folio preservation and folio migration in mm/memfd_luo.c. Because these modifications impact core MM/VFS subsystems and add new invariants reachable via memfd operations and the liveupdate ioctl interface, fuzzing is strongly warranted.",
"WorthFuzzing": true
}Instruction: You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.
IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.
================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.
- REACHABILITY IS THE PRIMARY GATE:
Fuzzing can only discover bugs in code that can actually execute in standard virtualized
environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
regardless of whether it adds assertions or complex logic.
- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
Patch authors routinely label changes as "cleanups", "refactorings", or state
"No functional change intended". Do NOT take these claims at face value.
Code refactorings that rearrange logic, introduce helper functions, or alter state management
in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
If reachable executable code is modified or refactored, it MUST be fuzzed.
- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
Even if the author believes the invariant always holds, fuzzing is essential to verify whether
an unusual sequence of operations can violate it.
================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:
- Non-kernel and non-executable changes:
* Modifications to Documentation/, comments, or spelling fixes.
* User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
that do not affect the compiled kernel image (vmlinux) or kernel modules.
* Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
that do not alter control flow or data structures.
* Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
* Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
* Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
physical PCI hot-unplug or manual sysfs driver unbinding.
* Code paths exclusive to architectures other than the target architecture.
================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
* Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
* Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
* Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
* Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).
================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:
- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
Do NOT list generic, ubiquitous functions called by almost every program in the corpus
(including, but not limited to: general memory allocators and deallocators, page fault
and trap handlers, or core synchronization primitives; this is not an exhaustive list).
Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
which severely dilutes fuzzing effort away from the actual changes.
- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
List functions that specifically implement the logic being added or altered, or direct API entrypoints
for the subsystem feature under review.
- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).
================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit d3dd9b6fca9a06703893cd89e47456874917efa8
Author: syz-cluster <triage@syzkaller.com>
Date: Wed Oct 28 01:44:06 2026 +0000
syz-cluster: applied patch under review
diff --git a/fs/inode.c b/fs/inode.c
index a9d37be390a173..635083c42419fc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -7,6 +7,7 @@
#include <linux/fs.h>
#include <linux/filelock.h>
#include <linux/mm.h>
+#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/hash.h>
#include <linux/swap.h>
@@ -818,6 +819,14 @@ static void evict(struct inode *inode)
inode_wait_for_writeback(inode);
spin_unlock(&inode->i_lock);
+ /*
+ * Whoever froze the mapping must hold an inode reference until it is
+ * unfrozen, so this should never happen. If it does, unfreeze it so
+ * the final truncate does not leak folios.
+ */
+ if (WARN_ON_ONCE(mapping_frozen(&inode->i_data)))
+ clear_bit(AS_FROZEN, &inode->i_data.flags);
+
if (op->evict_inode) {
op->evict_inode(inode);
} else {
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 73af18a3736706..9b9d0459f39922 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -209,6 +209,7 @@ enum mapping_flags {
AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
account usage to user cgroups */
+ AS_FROZEN = 11, /* index -> folio mapping must not change */
/* Bits 16-25 are used for FOLIO_ORDER */
AS_FOLIO_ORDER_BITS = 5,
AS_FOLIO_ORDER_MIN = 16,
@@ -344,6 +345,40 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
}
+/*
+ * A frozen mapping disallows any change to its i_pages: no folio can be added,
+ * removed, replaced (migration, swap out), split, or collapsed.
+ *
+ * Only the page cache is frozen, not the file. Operations that need to change
+ * the page cache fail with -EBUSY, e.g. a write or fault that needs to allocate
+ * a new folio. Others, like reading or writing (to pages already in i_pages),
+ * still work.
+ *
+ * Locking: the flag is flipped under the i_pages lock. The filesystem must
+ * ensure mapping_set_frozen() doesn't race with a truncate or fallocate, since
+ * those can fail if frozen mid-way.
+ *
+ * The mapping must be unfrozen before the inode is evicted.
+ */
+static inline void mapping_set_frozen(struct address_space *mapping)
+{
+ xa_lock_irq(&mapping->i_pages);
+ set_bit(AS_FROZEN, &mapping->flags);
+ xa_unlock_irq(&mapping->i_pages);
+}
+
+static inline void mapping_clear_frozen(struct address_space *mapping)
+{
+ xa_lock_irq(&mapping->i_pages);
+ clear_bit(AS_FROZEN, &mapping->flags);
+ xa_unlock_irq(&mapping->i_pages);
+}
+
+static inline bool mapping_frozen(const struct address_space *mapping)
+{
+ return test_bit(AS_FROZEN, &mapping->flags);
+}
+
static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
{
return mapping->gfp_mask;
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index a7c7a96a7cbf90..5b48598a7b9523 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -23,14 +23,6 @@
#define SHMEM_F_NORESERVE BIT(0)
/* Disallow swapping. */
#define SHMEM_F_LOCKED BIT(1)
-/*
- * Disallow growing, shrinking, or hole punching in the inode. Combined with
- * folio pinning, makes sure the inode's mapping stays fixed.
- *
- * In some ways similar to F_SEAL_GROW | F_SEAL_SHRINK, but can be removed and
- * isn't directly visible to userspace.
- */
-#define SHMEM_F_MAPPING_FROZEN BIT(2)
struct shmem_inode_info {
spinlock_t lock;
@@ -202,15 +194,6 @@ static inline bool shmem_file(struct file *file)
return shmem_mapping(file->f_mapping);
}
-/* Must be called with inode lock taken exclusive. */
-static inline void shmem_freeze(struct inode *inode, bool freeze)
-{
- if (freeze)
- SHMEM_I(inode)->flags |= SHMEM_F_MAPPING_FROZEN;
- else
- SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN;
-}
-
/*
* If fallocate(FALLOC_FL_KEEP_SIZE) has been used, there may be pages
* beyond i_size's notion of EOF, which fallocate has committed to reserving:
diff --git a/mm/filemap.c b/mm/filemap.c
index b74bc1e5015c6f..d040c69177f792 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -138,6 +138,7 @@ static void page_cache_delete(struct address_space *mapping,
nr = folio_nr_pages(folio);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), folio);
xas_store(&xas, shadow);
xas_init_marks(&xas);
@@ -284,6 +285,7 @@ static void page_cache_delete_batch(struct address_space *mapping,
int i = 0;
struct folio *folio;
+ VM_WARN_ON_ONCE(mapping_frozen(mapping));
mapping_set_update(&xas, mapping);
xas_for_each(&xas, folio, ULONG_MAX) {
if (i >= folio_batch_count(fbatch))
@@ -826,6 +828,7 @@ void replace_page_cache_folio(struct folio *old, struct folio *new)
mem_cgroup_replace_folio(old, new);
xas_lock_irq(&xas);
+ VM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), old);
xas_store(&xas, new);
old->mapping = NULL;
@@ -873,6 +876,10 @@ noinline int __filemap_add_folio(struct address_space *mapping,
void *entry, *old = NULL;
xas_lock_irq(&xas);
+ if (unlikely(mapping_frozen(mapping))) {
+ xas_set_err(&xas, -EBUSY);
+ goto unlock;
+ }
xas_for_each_conflict(&xas, entry) {
old = entry;
if (!xa_is_value(entry)) {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bd44d58e86845c..06d2f71ec74981 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3948,6 +3948,10 @@ int folio_check_splittable(struct folio *folio, unsigned int new_order,
if (!folio->mapping && !is_anon)
return -EBUSY;
+ /* Splitting would change a frozen mapping. */
+ if (!folio_test_anon(folio) && mapping_frozen(folio->mapping))
+ return -EBUSY;
+
/* order-1 is not supported for anonymous THP. */
if (is_anon && new_order == 1)
return -EINVAL;
@@ -4186,6 +4190,12 @@ static int __folio_freeze_split_file(struct folio *folio,
xas_lock_irq(&xas);
+ /* Can't change a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ ret = -EBUSY;
+ goto fail;
+ }
+
/*
* Check if the folio is present in page cache.
* We assume all tail are present too, if folio is there.
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index da91762f6358f2..5c78573f57c473 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2531,6 +2531,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
i_mmap_lock_read(mapping);
xas_lock_irq(&xas);
+ /* Can't collapse folios in a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ result = SCAN_FAIL;
+ goto immap_locked;
+ }
+
xas_set(&xas, start);
for (index = start; index < end; index++) {
if (!xas_next(&xas)) {
@@ -2582,6 +2588,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
}
} else {
xas_lock_irq(&xas);
+ /* Can't collapse folios in a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ xas_unlock_irq(&xas);
+ result = SCAN_FAIL;
+ goto rollback;
+ }
}
if (is_shmem) {
diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index 59de210bee5f9e..ec5abd41ecb8ba 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -77,26 +77,127 @@
#include <linux/kexec_handover.h>
#include <linux/kho/abi/memfd.h>
#include <linux/liveupdate.h>
+#include <linux/migrate.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/signal.h>
#include <linux/shmem_fs.h>
+#include <linux/swap.h>
#include <linux/vmalloc.h>
#include <linux/memfd.h>
+#include <linux/pagemap.h>
#include <uapi/linux/memfd.h>
#include "internal.h"
+static void memfd_luo_put_folios(const struct memfd_luo_folio_ser *folios_ser,
+ u64 nr_folios)
+{
+ u64 i;
+
+ for (i = 0; i < nr_folios; i++) {
+ const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+ struct folio *folio;
+
+ if (!pfolio->pfn)
+ continue;
+
+ folio = pfn_folio(pfolio->pfn);
+
+ kho_unpreserve_folio(folio);
+ folio_put(folio);
+ }
+}
+
+/* How many times to retry isolating a folio someone else has isolated. */
+#define MEMFD_LUO_MIGRATE_RETRIES 3
+
+/*
+ * Move a folio out of ZONE_MOVABLE or CMA, so it can be held until the next
+ * kernel. Called with a reference on the unlocked folio, which is always
+ * dropped. The caller must look up the folio again afterwards.
+ *
+ * Returns 0 on success, -EBUSY if the folio could not be isolated (e.g.
+ * because someone else has it isolated right now), or -ENOMEM if migration
+ * failed.
+ */
+static int memfd_luo_migrate_folio(struct folio *folio)
+{
+ struct migration_target_control mtc = {
+ .nid = NUMA_NO_NODE,
+ /* Not movable, so the target is neither in ZONE_MOVABLE nor CMA. */
+ .gfp_mask = GFP_USER | __GFP_NOWARN,
+ .reason = MR_LONGTERM_PIN,
+ };
+ LIST_HEAD(source);
+ bool isolated;
+
+ /* Flush per-CPU LRU batches holding the folio so isolation works. */
+ lru_cache_drain_for_folio(folio, 1, NULL);
+ isolated = isolate_folio_to_list(folio, &source);
+ /* Isolation holds its own reference. */
+ folio_put(folio);
+ if (!isolated)
+ return -EBUSY;
+
+ if (migrate_pages(&source, alloc_migration_target, NULL,
+ (unsigned long)&mtc, MIGRATE_SYNC, MR_LONGTERM_PIN,
+ NULL)) {
+ putback_movable_pages(&source);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static int memfd_luo_preserve_folio(struct folio *folio,
+ struct memfd_luo_folio_ser *pfolio)
+{
+ int err;
+
+ err = kho_preserve_folio(folio);
+ if (err)
+ return err;
+
+ /*
+ * A dirty folio is one which has been written to. A clean folio
+ * is its opposite. Since a clean folio does not carry user
+ * data, it can be freed by page reclaim under memory pressure.
+ *
+ * Saving the dirty flag at prepare() time doesn't work since it
+ * can change later. Saving it at freeze() also won't work
+ * because the dirty bit is normally synced at unmap and there
+ * might still be a mapping of the file at freeze().
+ *
+ * To see why this is a problem, say a folio is clean at
+ * preserve, but gets dirtied later. The pfolio flags will mark
+ * it as clean. After retrieve, the next kernel might try to
+ * reclaim this folio under memory pressure, losing user data.
+ *
+ * Unconditionally mark it dirty to avoid this problem. This
+ * comes at the cost of making clean folios un-reclaimable after
+ * live update.
+ */
+ folio_mark_dirty(folio);
+
+ pfolio->pfn = folio_pfn(folio);
+ pfolio->flags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;
+ pfolio->index = folio->index;
+
+ return 0;
+}
+
static int memfd_luo_preserve_folios(struct file *file,
struct kho_vmalloc *kho_vmalloc,
struct memfd_luo_folio_ser **out_folios_ser,
u64 *nr_foliosp)
{
+ struct memfd_luo_folio_ser *folios_ser, *shrunk;
struct inode *inode = file_inode(file);
- struct memfd_luo_folio_ser *folios_ser;
- unsigned int max_folios;
- long i, size, nr_pinned;
- struct folio **folios;
- int err = -EINVAL;
- pgoff_t offset;
- u64 nr_folios;
+ u64 nr_folios = 0, max_folios;
+ int err, busy_retries = 0;
+ unsigned int pin_flags;
+ pgoff_t index = 0, end;
+ loff_t size;
size = i_size_read(inode);
/*
@@ -113,99 +214,77 @@ static int memfd_luo_preserve_folios(struct file *file,
* Guess the number of folios based on inode size. Real number might end
* up being smaller if there are higher order folios.
*/
- max_folios = PAGE_ALIGN(size) / PAGE_SIZE;
- folios = kvmalloc_objs(*folios, max_folios);
- if (!folios)
+ end = DIV_ROUND_UP_ULL(size, PAGE_SIZE);
+ max_folios = end;
+ folios_ser = vmalloc_array(max_folios, sizeof(*folios_ser));
+ if (!folios_ser)
return -ENOMEM;
/*
- * Pin the folios so they don't move around behind our back. This also
- * ensures none of the folios are in CMA -- which ensures they don't
- * fall in KHO scratch memory. It also moves swapped out folios back to
- * memory.
+ * The folios are held until the next kernel, so keep newly allocated
+ * ones out of ZONE_MOVABLE and CMA -- which also ensures they don't
+ * fall in KHO bootmem. Existing ones are migrated below.
*
- * A side effect of doing this is that it allocates a folio for all
- * indices in the file. This might waste memory on sparse memfds. If
- * that is really a problem in the future, we can have a
- * memfd_pin_folios() variant that does not allocate a page on empty
- * slots.
+ * A side effect of this is that it allocates a folio for all indices in
+ * the file. This might waste memory on sparse memfds. If that is really
+ * a problem in the future, this loop can be taught to skip empty slots.
*/
- nr_pinned = memfd_pin_folios(file, 0, size - 1, folios, max_folios,
- &offset);
- if (nr_pinned < 0) {
- err = nr_pinned;
- pr_err("failed to pin folios: %d\n", err);
- goto err_free_folios;
- }
- nr_folios = nr_pinned;
+ pin_flags = memalloc_pin_save();
+ while (index < end) {
+ struct folio *folio;
- folios_ser = vcalloc(nr_folios, sizeof(*folios_ser));
- if (!folios_ser) {
- err = -ENOMEM;
- goto err_unpin;
- }
+ cond_resched();
- for (i = 0; i < nr_folios; i++) {
- struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
- struct folio *folio = folios[i];
+ if (fatal_signal_pending(current)) {
+ err = -EINTR;
+ goto err_restore;
+ }
+
+ if (WARN_ON_ONCE(nr_folios >= max_folios)) {
+ err = -EINVAL;
+ goto err_restore;
+ }
- err = kho_preserve_folio(folio);
+ err = shmem_get_folio(inode, index, 0, &folio, SGP_CACHE);
if (err)
- goto err_unpreserve;
-
- folio_lock(folio);
-
- /*
- * A dirty folio is one which has been written to. A clean folio
- * is its opposite. Since a clean folio does not carry user
- * data, it can be freed by page reclaim under memory pressure.
- *
- * Saving the dirty flag at prepare() time doesn't work since it
- * can change later. Saving it at freeze() also won't work
- * because the dirty bit is normally synced at unmap and there
- * might still be a mapping of the file at freeze().
- *
- * To see why this is a problem, say a folio is clean at
- * preserve, but gets dirtied later. The pfolio flags will mark
- * it as clean. After retrieve, the next kernel might try to
- * reclaim this folio under memory pressure, losing user data.
- *
- * Unconditionally mark it dirty to avoid this problem. This
- * comes at the cost of making clean folios un-reclaimable after
- * live update.
- */
- folio_mark_dirty(folio);
-
- /*
- * If the folio is not uptodate, it was fallocated but never
- * used. Saving this flag at prepare() doesn't work since it
- * might change later when someone uses the folio.
- *
- * Since we have taken the performance penalty of allocating,
- * zeroing, and pinning all the folios in the holes, take a bit
- * more and zero all non-uptodate folios too.
- *
- * NOTE: For someone looking to improve preserve performance,
- * this is a good place to look.
- */
- if (!folio_test_uptodate(folio)) {
- folio_zero_range(folio, 0, folio_size(folio));
- flush_dcache_folio(folio);
- folio_mark_uptodate(folio);
+ goto err_restore;
+
+ if (unlikely(!folio_is_longterm_pinnable(folio))) {
+ folio_unlock(folio);
+ err = memfd_luo_migrate_folio(folio);
+ /* Someone else might have it isolated, retry a bit. */
+ if (err == -EBUSY && ++busy_retries < MEMFD_LUO_MIGRATE_RETRIES)
+ continue;
+ if (err)
+ goto err_restore;
+ continue;
}
+ err = memfd_luo_preserve_folio(folio, &folios_ser[nr_folios]);
+ index = folio_next_index(folio);
folio_unlock(folio);
-
- pfolio->pfn = folio_pfn(folio);
- pfolio->flags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;
- pfolio->index = folio->index;
+ if (err) {
+ folio_put(folio);
+ goto err_restore;
+ }
+ nr_folios++;
+ busy_retries = 0;
}
+ memalloc_pin_restore(pin_flags);
+
+ /*
+ * Free the unused tail so it doesn't get preserved. If vrealloc fails,
+ * the folios_ser is still valid.
+ */
+ shrunk = vrealloc(folios_ser, array_size(nr_folios, sizeof(*folios_ser)),
+ GFP_KERNEL);
+ if (shrunk)
+ folios_ser = shrunk;
err = kho_preserve_vmalloc(folios_ser, kho_vmalloc);
if (err)
- goto err_unpreserve;
+ goto err_put;
- kvfree(folios);
*nr_foliosp = nr_folios;
*out_folios_ser = folios_ser;
@@ -216,15 +295,11 @@ static int memfd_luo_preserve_folios(struct file *file,
*/
return 0;
-err_unpreserve:
- for (i = i - 1; i >= 0; i--)
- kho_unpreserve_folio(folios[i]);
+err_restore:
+ memalloc_pin_restore(pin_flags);
+err_put:
+ memfd_luo_put_folios(folios_ser, nr_folios);
vfree(folios_ser);
-err_unpin:
- unpin_folios(folios, nr_folios);
-err_free_folios:
- kvfree(folios);
-
return err;
}
@@ -232,26 +307,11 @@ static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,
struct memfd_luo_folio_ser *folios_ser,
u64 nr_folios)
{
- long i;
-
if (!nr_folios)
return;
kho_unpreserve_vmalloc(kho_vmalloc);
-
- for (i = 0; i < nr_folios; i++) {
- const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
- struct folio *folio;
-
- if (!pfolio->pfn)
- continue;
-
- folio = pfn_folio(pfolio->pfn);
-
- kho_unpreserve_folio(folio);
- unpin_folio(folio);
- }
-
+ memfd_luo_put_folios(folios_ser, nr_folios);
vfree(folios_ser);
}
@@ -264,7 +324,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
int err = 0, seals;
inode_lock(inode);
- shmem_freeze(inode, true);
/* Allocate the main serialization structure in preserved memory */
ser = kho_alloc_preserve(sizeof(*ser));
@@ -288,15 +347,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
ser->pos = args->file->f_pos;
inode_size = i_size_read(inode);
- /*
- * memfd_pin_folios() caps at UINT_MAX folios; refuse larger
- * files to avoid silently preserving only a prefix.
- */
- if (DIV_ROUND_UP_ULL(inode_size, PAGE_SIZE) > UINT_MAX) {
- err = -EFBIG;
- goto err_free_ser;
- }
-
ser->size = inode_size;
ser->seals = seals;
@@ -305,6 +355,12 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
if (err)
goto err_free_ser;
+ /*
+ * All the folios in the file are now stable. Freeze the mapping to make
+ * sure new ones can't be added.
+ */
+ mapping_set_frozen(inode->i_mapping);
+
ser->nr_folios = nr_folios;
inode_unlock(inode);
@@ -316,7 +372,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
err_free_ser:
kho_unpreserve_free(ser);
err_unlock:
- shmem_freeze(inode, false);
inode_unlock(inode);
return err;
}
@@ -348,7 +403,7 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
return;
inode_lock(inode);
- shmem_freeze(inode, false);
+ mapping_clear_frozen(inode->i_mapping);
ser = phys_to_virt(args->serialized_data);
diff --git a/mm/migrate.c b/mm/migrate.c
index d649a6cfce6c09..6ce01871d72e39 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -614,10 +614,16 @@ static int __folio_migrate_mapping(struct address_space *mapping,
oldzone = folio_zone(folio);
newzone = folio_zone(newfolio);
- if (folio_test_swapcache(folio))
+ if (folio_test_swapcache(folio)) {
ci = swap_cluster_get_and_lock_irq(folio);
- else
+ } else {
xas_lock_irq(&xas);
+ /* Can't replace folios in a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ xas_unlock_irq(&xas);
+ return -EBUSY;
+ }
+ }
if (!folio_ref_freeze(folio, expected_count)) {
if (ci)
@@ -750,6 +756,10 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
return rc;
xas_lock_irq(&xas);
+ if (mapping_frozen(mapping)) {
+ xas_unlock_irq(&xas);
+ return -EBUSY;
+ }
if (!folio_ref_freeze(src, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
diff --git a/mm/shmem.c b/mm/shmem.c
index 13e0786436cda1..1c70fd306bec21 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1121,6 +1121,10 @@ int shmem_add_to_page_cache(struct folio *folio,
do {
iter = swap;
xas_lock_irq(&xas);
+ if (unlikely(mapping_frozen(mapping))) {
+ xas_set_err(&xas, -EBUSY);
+ goto unlock;
+ }
xas_for_each_conflict(&xas, entry) {
/*
* The range must either be empty, or filled with
@@ -1345,6 +1349,10 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
if (lend == -1)
end = -1; /* unsigned, so actually very big */
+ /* Callers must not try to truncate a frozen mapping. */
+ if (WARN_ON_ONCE(mapping_frozen(mapping)))
+ return;
+
if (info->fallocend > start && info->fallocend <= end && !unfalloc)
info->fallocend = start;
@@ -1562,8 +1570,6 @@ static int shmem_setattr(struct mnt_idmap *idmap,
return -EPERM;
if (newsize != oldsize) {
- if (info->flags & SHMEM_F_MAPPING_FROZEN)
- return -EPERM;
error = shmem_reacct_size(SHMEM_I(inode)->flags,
oldsize, newsize);
if (error)
@@ -1575,6 +1581,11 @@ static int shmem_setattr(struct mnt_idmap *idmap,
}
if (newsize <= oldsize) {
loff_t holebegin = round_up(newsize, PAGE_SIZE);
+
+ /* No truncation allowed on a frozen mapping. */
+ if (mapping_frozen(inode->i_mapping))
+ return -EBUSY;
+
if (oldsize > holebegin)
unmap_mapping_range(inode->i_mapping,
holebegin, 0, 1);
@@ -1822,6 +1833,10 @@ int shmem_writeout(struct swap_io_ctx *ctx, struct folio *folio,
if ((info->flags & SHMEM_F_LOCKED) || sbinfo->noswap)
goto redirty;
+ /* Swapping out would replace the folio in a frozen mapping. */
+ if (mapping_frozen(mapping))
+ goto redirty;
+
if (!total_swap_pages)
goto redirty;
@@ -2483,6 +2498,13 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
if (softleaf_is_poison_marker(index_entry))
return -EIO;
+ /*
+ * Swapping in would change the i_pages of a frozen mapping. A frozen
+ * mapping should not have swap entries in the first place.
+ */
+ if (unlikely(mapping_frozen(mapping)))
+ return -EBUSY;
+
si = get_swap_device(index_entry);
order = shmem_confirm_swap(mapping, index, index_entry);
if (IS_ERR_OR_NULL(si)) {
@@ -3463,10 +3485,6 @@ shmem_write_begin(const struct kiocb *iocb, struct address_space *mapping,
return -EPERM;
}
- if (unlikely((info->flags & SHMEM_F_MAPPING_FROZEN) &&
- pos + len > inode->i_size))
- return -EPERM;
-
ret = shmem_get_folio(inode, index, pos + len, &folio, SGP_WRITE);
if (ret)
return ret;
@@ -3841,8 +3859,8 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
inode_lock(inode);
- if (info->flags & SHMEM_F_MAPPING_FROZEN) {
- error = -EPERM;
+ if (mapping_frozen(inode->i_mapping)) {
+ error = -EBUSY;
goto out;
}
diff --git a/mm/truncate.c b/mm/truncate.c
index 733d2713a875a5..6512f460a28e94 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -171,6 +171,8 @@ int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
{
if (folio->mapping != mapping)
return -EIO;
+ if (mapping_frozen(mapping))
+ return -EBUSY;
truncate_cleanup_folio(folio);
filemap_remove_folio(folio);
@@ -367,6 +369,8 @@ long mapping_evict_folio(struct address_space *mapping, struct folio *folio)
return 0;
if (folio_test_dirty(folio) || folio_test_writeback(folio))
return 0;
+ if (mapping_frozen(mapping))
+ return 0;
/* The refcount will be elevated if any page in the folio is mapped */
if (folio_ref_count(folio) >
folio_nr_pages(folio) + folio_has_private(folio) + 1)
@@ -419,6 +423,13 @@ void truncate_inode_pages_range(struct address_space *mapping,
if (mapping_empty(mapping))
return;
+ /*
+ * Callers must not try to truncate a frozen mapping. Filesystems that
+ * support frozen mappings must refuse shrinking and hole punching
+ * before getting here.
+ */
+ if (WARN_ON_ONCE(mapping_frozen(mapping)))
+ return;
/*
* 'start' and 'end' always covers the range of folios to be fully
* truncated, with both boundaries aligned inwards to 1 << min_order.
@@ -668,6 +679,9 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ if (mapping_frozen(mapping))
+ return -EBUSY;
+
if (folio_mapped(folio))
unmap_mapping_folio(folio);
BUG_ON(folio_mapped(folio));
@@ -682,7 +696,7 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
- if (folio_test_dirty(folio))
+ if (folio_test_dirty(folio) || mapping_frozen(mapping))
goto failed;
BUG_ON(folio_has_private(folio));
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9959ca158ce835..86ef233e8752ee 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -766,6 +766,9 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
} else {
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
+ /* Can't remove folios from a frozen mapping. */
+ if (mapping_frozen(mapping))
+ goto cannot_free;
}
/*
|
| 3/2 | 2026/10/28 01:44 | llm | patch-evaluator |
2mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12655 output: 33 thoughts: 241 Thoughts: **Analyzing a Kernel Patch for Potential Fuzzing Targets** Okay, let's take a look at this patch and decide if it's worth our time to throw syzkaller at it. The first step, as always, is to understand exactly what this patch is changing. It looks like they're introducing `AS_FROZEN` into `enum mapping_flags` in `include/linux/pagemap.h`, and adding a few supporting functions: `mapping_set_frozen`, `mapping_clear_frozen`, and `mapping_frozen`. And it seems like this new flag is replacing an older, `SHMEM_F_MAPPING_FROZEN`. That's interesting, suggesting a move towards generalization. The files modified are quite a range: `fs/inode.c`, `include/linux/pagemap.h`, `include/linux/shmem_fs.h`, `mm/filemap.c`, `mm/huge_memory.c`, `mm/khugepaged.c`, `mm/memfd_luo.c`, `mm/migrate.c`, `mm/shmem.c`, `mm/truncate.c`, and `mm/vmscan.c`. That's a decent spread. It touches some core memory management and file system code. Hold on... I'm slightly unfamiliar with `mm/memfd_luo.c`. Let me quickly check the context of that file using `grepper` or `read-file` to refresh my memory on the interactions there. It's important to understand the specific functionalities within these files, to give me a more accurate judgement about potential fuzzing targets. |
| 4/2 | 2026/10/28 01:46 | tool | grepper |
0mArgs:{
"Expression": "memfd_luo",
"PathPrefixes": [
"mm/",
"include/"
]
}Results: {
"Output": "include/linux/kho/abi/memfd.h-22- *\ninclude/linux/kho/abi/memfd.h:23: * The state is serialized into a packed structure `struct memfd_luo_ser`\ninclude/linux/kho/abi/memfd.h-24- * which is handed over to the next kernel via the KHO mechanism.\n--\ninclude/linux/kho/abi/memfd.h-47-/**\ninclude/linux/kho/abi/memfd.h:48: * struct memfd_luo_folio_ser - Serialized state of a single folio.\ninclude/linux/kho/abi/memfd.h-49- * @pfn: The page frame number of the folio.\n--\ninclude/linux/kho/abi/memfd.h-52- */\ninclude/linux/kho/abi/memfd.h:53:struct memfd_luo_folio_ser {\ninclude/linux/kho/abi/memfd.h-54-\tu64 pfn:52;\n--\ninclude/linux/kho/abi/memfd.h-70-/**\ninclude/linux/kho/abi/memfd.h:71: * struct memfd_luo_ser - Main serialization structure for a memfd.\ninclude/linux/kho/abi/memfd.h-72- * @pos: The file's current position (f_pos).\n--\ninclude/linux/kho/abi/memfd.h-78- * @folios: KHO vmalloc descriptor pointing to the array of\ninclude/linux/kho/abi/memfd.h:79: * struct memfd_luo_folio_ser.\ninclude/linux/kho/abi/memfd.h-80- */\ninclude/linux/kho/abi/memfd.h:81:struct memfd_luo_ser {\ninclude/linux/kho/abi/memfd.h-82-\tu64 pos;\n--\nmm/Makefile=103=obj-$(CONFIG_PAGE_COUNTER) += page_counter.o\nmm/Makefile:104:obj-$(CONFIG_LIVEUPDATE_MEMFD) += memfd_luo.o\nmm/Makefile-105-obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o\n--\nmm/memfd_luo.c-91-\nmm/memfd_luo.c:92:static void memfd_luo_put_folios(const struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-93-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-97-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:98:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-99-\t\tstruct folio *folio;\n--\nmm/memfd_luo.c-122- */\nmm/memfd_luo.c:123:static int memfd_luo_migrate_folio(struct folio *folio)\nmm/memfd_luo.c-124-{\n--\nmm/memfd_luo.c-151-\nmm/memfd_luo.c:152:static int memfd_luo_preserve_folio(struct folio *folio,\nmm/memfd_luo.c:153:\t\t\t\t struct memfd_luo_folio_ser *pfolio)\nmm/memfd_luo.c-154-{\n--\nmm/memfd_luo.c-188-\nmm/memfd_luo.c:189:static int memfd_luo_preserve_folios(struct file *file,\nmm/memfd_luo.c-190-\t\t\t\t struct kho_vmalloc *kho_vmalloc,\nmm/memfd_luo.c:191:\t\t\t\t struct memfd_luo_folio_ser **out_folios_ser,\nmm/memfd_luo.c-192-\t\t\t\t u64 *nr_foliosp)\nmm/memfd_luo.c-193-{\nmm/memfd_luo.c:194:\tstruct memfd_luo_folio_ser *folios_ser, *shrunk;\nmm/memfd_luo.c-195-\tstruct inode *inode = file_inode(file);\n--\nmm/memfd_luo.c-253-\t\t\tfolio_unlock(folio);\nmm/memfd_luo.c:254:\t\t\terr = memfd_luo_migrate_folio(folio);\nmm/memfd_luo.c-255-\t\t\t/* Someone else might have it isolated, retry a bit. */\n--\nmm/memfd_luo.c-262-\nmm/memfd_luo.c:263:\t\terr = memfd_luo_preserve_folio(folio, \u0026folios_ser[nr_folios]);\nmm/memfd_luo.c-264-\t\tindex = folio_next_index(folio);\n--\nmm/memfd_luo.c-300-err_put:\nmm/memfd_luo.c:301:\tmemfd_luo_put_folios(folios_ser, nr_folios);\nmm/memfd_luo.c-302-\tvfree(folios_ser);\n--\nmm/memfd_luo.c-305-\nmm/memfd_luo.c:306:static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,\nmm/memfd_luo.c:307:\t\t\t\t\tstruct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-308-\t\t\t\t\tu64 nr_folios)\n--\nmm/memfd_luo.c-313-\tkho_unpreserve_vmalloc(kho_vmalloc);\nmm/memfd_luo.c:314:\tmemfd_luo_put_folios(folios_ser, nr_folios);\nmm/memfd_luo.c-315-\tvfree(folios_ser);\n--\nmm/memfd_luo.c-317-\nmm/memfd_luo.c:318:static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-319-{\nmm/memfd_luo.c-320-\tstruct inode *inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:321:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c:322:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-323-\tu64 nr_folios, inode_size;\n--\nmm/memfd_luo.c-352-\nmm/memfd_luo.c:353:\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\nmm/memfd_luo.c-354-\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n--\nmm/memfd_luo.c-378-\nmm/memfd_luo.c:379:static int memfd_luo_freeze(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-380-{\nmm/memfd_luo.c:381:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-382-\n--\nmm/memfd_luo.c-396-\nmm/memfd_luo.c:397:static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-398-{\nmm/memfd_luo.c-399-\tstruct inode *inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:400:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-401-\n--\nmm/memfd_luo.c-409-\nmm/memfd_luo.c:410:\tmemfd_luo_unpreserve_folios(\u0026ser-\u003efolios, args-\u003eprivate_data,\nmm/memfd_luo.c-411-\t\t\t\t ser-\u003enr_folios);\n--\nmm/memfd_luo.c-416-\nmm/memfd_luo.c:417:static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-418-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-422-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:423:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-424-\t\tstruct folio *folio;\n--\nmm/memfd_luo.c-441-\nmm/memfd_luo.c:442:static void memfd_luo_finish(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-443-{\nmm/memfd_luo.c:444:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c:445:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-446-\n--\nmm/memfd_luo.c-463-\nmm/memfd_luo.c:464:\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\nmm/memfd_luo.c-465-\t\tvfree(folios_ser);\n--\nmm/memfd_luo.c-471-\nmm/memfd_luo.c:472:static int memfd_luo_retrieve_folios(struct file *file,\nmm/memfd_luo.c:473:\t\t\t\t struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-474-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-483-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:484:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-485-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-555-\tfor (long j = i + 1; j \u003c nr_folios; j++) {\nmm/memfd_luo.c:556:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[j];\nmm/memfd_luo.c-557-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-572-\nmm/memfd_luo.c:573:static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-574-{\nmm/memfd_luo.c:575:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c:576:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-577-\tstruct file *file;\n--\nmm/memfd_luo.c-616-\nmm/memfd_luo.c:617:\t\terr = memfd_luo_retrieve_folios(file, folios_ser, ser-\u003enr_folios);\nmm/memfd_luo.c-618-\t\tvfree(folios_ser);\n--\nmm/memfd_luo.c-634-\nmm/memfd_luo.c:635:static bool memfd_luo_can_preserve(struct liveupdate_file_handler *handler,\nmm/memfd_luo.c-636-\t\t\t\t struct file *file)\n--\nmm/memfd_luo.c-642-\nmm/memfd_luo.c:643:static unsigned long memfd_luo_get_id(struct file *file)\nmm/memfd_luo.c-644-{\n--\nmm/memfd_luo.c-647-\nmm/memfd_luo.c:648:static const struct liveupdate_file_ops memfd_luo_file_ops = {\nmm/memfd_luo.c:649:\t.freeze = memfd_luo_freeze,\nmm/memfd_luo.c:650:\t.finish = memfd_luo_finish,\nmm/memfd_luo.c:651:\t.retrieve = memfd_luo_retrieve,\nmm/memfd_luo.c:652:\t.preserve = memfd_luo_preserve,\nmm/memfd_luo.c:653:\t.unpreserve = memfd_luo_unpreserve,\nmm/memfd_luo.c:654:\t.can_preserve = memfd_luo_can_preserve,\nmm/memfd_luo.c:655:\t.get_id = memfd_luo_get_id,\nmm/memfd_luo.c-656-\t.owner = THIS_MODULE,\n--\nmm/memfd_luo.c-658-\nmm/memfd_luo.c:659:static struct liveupdate_file_handler memfd_luo_handler = {\nmm/memfd_luo.c:660:\t.ops = \u0026memfd_luo_file_ops,\nmm/memfd_luo.c-661-\t.compatible = MEMFD_LUO_FH_COMPATIBLE,\n--\nmm/memfd_luo.c-663-\nmm/memfd_luo.c:664:static int __init memfd_luo_init(void)\nmm/memfd_luo.c-665-{\nmm/memfd_luo.c:666:\tint err = liveupdate_register_file_handler(\u0026memfd_luo_handler);\nmm/memfd_luo.c-667-\n--\nmm/memfd_luo.c-676-}\nmm/memfd_luo.c:677:late_initcall(memfd_luo_init);\n"
} |
| 5/2 | 2026/10/28 01:46 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 17030 output: 29 thoughts: 35 Thoughts: Okay, let's dive into this code. **Investigating the `mapping_set_frozen` Callers and Usage** Alright, I need to get a better handle on this `mapping_set_frozen` function. I want to understand its impact and where it's being utilized within the codebase. My plan is straightforward: I'll start with a classic approach. I will do a code-wide search, a `grep` in the code, for the string `mapping_set_frozen`. That should give me a solid list of all the places it's called or referenced. With this list, I can start analyzing the relationships and dependencies. |
| 6/2 | 2026/10/28 01:46 | tool | grepper |
0mArgs:{
"Expression": "mapping_set_frozen|mapping_clear_frozen|mapping_frozen"
}Results: {
"Output": "fs/inode.c=800=static void evict(struct inode *inode)\n--\nfs/inode.c-826-\t */\nfs/inode.c:827:\tif (WARN_ON_ONCE(mapping_frozen(\u0026inode-\u003ei_data)))\nfs/inode.c-828-\t\tclear_bit(AS_FROZEN, \u0026inode-\u003ei_data.flags);\n--\ninclude/linux/pagemap.h=343=static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct address_space *mapping)\n--\ninclude/linux/pagemap.h-357- * Locking: the flag is flipped under the i_pages lock. The filesystem must\ninclude/linux/pagemap.h:358: * ensure mapping_set_frozen() doesn't race with a truncate or fallocate, since\ninclude/linux/pagemap.h-359- * those can fail if frozen mid-way.\n--\ninclude/linux/pagemap.h-362- */\ninclude/linux/pagemap.h:363:static inline void mapping_set_frozen(struct address_space *mapping)\ninclude/linux/pagemap.h-364-{\n--\ninclude/linux/pagemap.h-369-\ninclude/linux/pagemap.h:370:static inline void mapping_clear_frozen(struct address_space *mapping)\ninclude/linux/pagemap.h-371-{\n--\ninclude/linux/pagemap.h-376-\ninclude/linux/pagemap.h:377:static inline bool mapping_frozen(const struct address_space *mapping)\ninclude/linux/pagemap.h-378-{\n--\nmm/filemap.c=129=static void page_cache_delete(struct address_space *mapping,\n--\nmm/filemap.c-140-\tVM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);\nmm/filemap.c:141:\tVM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), folio);\nmm/filemap.c-142-\n--\nmm/filemap.c=280=static void page_cache_delete_batch(struct address_space *mapping,\n--\nmm/filemap.c-287-\nmm/filemap.c:288:\tVM_WARN_ON_ONCE(mapping_frozen(mapping));\nmm/filemap.c-289-\tmapping_set_update(\u0026xas, mapping);\n--\nmm/filemap.c=813=void replace_page_cache_folio(struct folio *old, struct folio *new)\n--\nmm/filemap.c-830-\txas_lock_irq(\u0026xas);\nmm/filemap.c:831:\tVM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), old);\nmm/filemap.c-832-\txas_store(\u0026xas, new);\n--\nmm/filemap.c=851=noinline int __filemap_add_folio(struct address_space *mapping,\n--\nmm/filemap.c-878-\t\txas_lock_irq(\u0026xas);\nmm/filemap.c:879:\t\tif (unlikely(mapping_frozen(mapping))) {\nmm/filemap.c-880-\t\t\txas_set_err(\u0026xas, -EBUSY);\n--\nmm/huge_memory.c=3934=int folio_check_splittable(struct folio *folio, unsigned int new_order,\n--\nmm/huge_memory.c-3951-\t/* Splitting would change a frozen mapping. */\nmm/huge_memory.c:3952:\tif (!folio_test_anon(folio) \u0026\u0026 mapping_frozen(folio-\u003emapping))\nmm/huge_memory.c-3953-\t\treturn -EBUSY;\n--\nmm/huge_memory.c=4124=static int __folio_freeze_split_file(struct folio *folio,\n--\nmm/huge_memory.c-4193-\t/* Can't change a frozen mapping. */\nmm/huge_memory.c:4194:\tif (mapping_frozen(mapping)) {\nmm/huge_memory.c-4195-\t\tret = -EBUSY;\n--\nmm/khugepaged.c=2229=static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\n--\nmm/khugepaged.c-2534-\t\t/* Can't collapse folios in a frozen mapping. */\nmm/khugepaged.c:2535:\t\tif (mapping_frozen(mapping)) {\nmm/khugepaged.c-2536-\t\t\tresult = SCAN_FAIL;\n--\nmm/khugepaged.c-2591-\t\t/* Can't collapse folios in a frozen mapping. */\nmm/khugepaged.c:2592:\t\tif (mapping_frozen(mapping)) {\nmm/khugepaged.c-2593-\t\t\txas_unlock_irq(\u0026xas);\n--\nmm/memfd_luo.c=318=static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\n--\nmm/memfd_luo.c-361-\t */\nmm/memfd_luo.c:362:\tmapping_set_frozen(inode-\u003ei_mapping);\nmm/memfd_luo.c-363-\n--\nmm/memfd_luo.c=397=static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)\n--\nmm/memfd_luo.c-405-\tinode_lock(inode);\nmm/memfd_luo.c:406:\tmapping_clear_frozen(inode-\u003ei_mapping);\nmm/memfd_luo.c-407-\n--\nmm/migrate.c=583=static int __folio_migrate_mapping(struct address_space *mapping,\n--\nmm/migrate.c-621-\t\t/* Can't replace folios in a frozen mapping. */\nmm/migrate.c:622:\t\tif (mapping_frozen(mapping)) {\nmm/migrate.c-623-\t\t\txas_unlock_irq(\u0026xas);\n--\nmm/migrate.c=745=int migrate_huge_page_move_mapping(struct address_space *mapping,\n--\nmm/migrate.c-758-\txas_lock_irq(\u0026xas);\nmm/migrate.c:759:\tif (mapping_frozen(mapping)) {\nmm/migrate.c-760-\t\txas_unlock_irq(\u0026xas);\n--\nmm/shmem.c=1100=int shmem_add_to_page_cache(struct folio *folio,\n--\nmm/shmem.c-1123-\t\txas_lock_irq(\u0026xas);\nmm/shmem.c:1124:\t\tif (unlikely(mapping_frozen(mapping))) {\nmm/shmem.c-1125-\t\t\txas_set_err(\u0026xas, -EBUSY);\n--\nmm/shmem.c=1334=static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,\n--\nmm/shmem.c-1352-\t/* Callers must not try to truncate a frozen mapping. */\nmm/shmem.c:1353:\tif (WARN_ON_ONCE(mapping_frozen(mapping)))\nmm/shmem.c-1354-\t\treturn;\n--\nmm/shmem.c=1544=static int shmem_setattr(struct mnt_idmap *idmap,\n--\nmm/shmem.c-1585-\t\t\t/* No truncation allowed on a frozen mapping. */\nmm/shmem.c:1586:\t\t\tif (mapping_frozen(inode-\u003ei_mapping))\nmm/shmem.c-1587-\t\t\t\treturn -EBUSY;\n--\nmm/shmem.c=1822=int shmem_writeout(struct swap_io_ctx *ctx, struct folio *folio,\n--\nmm/shmem.c-1836-\t/* Swapping out would replace the folio in a frozen mapping. */\nmm/shmem.c:1837:\tif (mapping_frozen(mapping))\nmm/shmem.c-1838-\t\tgoto redirty;\n--\nmm/shmem.c=2477=static int shmem_swapin_folio(struct inode *inode, pgoff_t index,\n--\nmm/shmem.c-2504-\t */\nmm/shmem.c:2505:\tif (unlikely(mapping_frozen(mapping)))\nmm/shmem.c-2506-\t\treturn -EBUSY;\n--\nmm/shmem.c=3846=static long shmem_fallocate(struct file *file, int mode, loff_t offset,\n--\nmm/shmem.c-3861-\nmm/shmem.c:3862:\tif (mapping_frozen(inode-\u003ei_mapping)) {\nmm/shmem.c-3863-\t\terror = -EBUSY;\n--\nmm/truncate.c=170=int truncate_inode_folio(struct address_space *mapping, struct folio *folio)\n--\nmm/truncate.c-173-\t\treturn -EIO;\nmm/truncate.c:174:\tif (mapping_frozen(mapping))\nmm/truncate.c-175-\t\treturn -EBUSY;\n--\nmm/truncate.c=365=long mapping_evict_folio(struct address_space *mapping, struct folio *folio)\n--\nmm/truncate.c-371-\t\treturn 0;\nmm/truncate.c:372:\tif (mapping_frozen(mapping))\nmm/truncate.c-373-\t\treturn 0;\n--\nmm/truncate.c=410=void truncate_inode_pages_range(struct address_space *mapping,\n--\nmm/truncate.c-430-\t */\nmm/truncate.c:431:\tif (WARN_ON_ONCE(mapping_frozen(mapping)))\nmm/truncate.c-432-\t\treturn;\n--\nmm/truncate.c=674=int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,\n--\nmm/truncate.c-681-\nmm/truncate.c:682:\tif (mapping_frozen(mapping))\nmm/truncate.c-683-\t\treturn -EBUSY;\n--\nmm/truncate.c-698-\txa_lock_irq(\u0026mapping-\u003ei_pages);\nmm/truncate.c:699:\tif (folio_test_dirty(folio) || mapping_frozen(mapping))\nmm/truncate.c-700-\t\tgoto failed;\n--\nmm/vmscan.c=754=static int __remove_mapping(struct address_space *mapping, struct folio *folio,\n--\nmm/vmscan.c-769-\t\t/* Can't remove folios from a frozen mapping. */\nmm/vmscan.c:770:\t\tif (mapping_frozen(mapping))\nmm/vmscan.c-771-\t\t\tgoto cannot_free;\n"
} |
| 7/2 | 2026/10/28 01:46 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 20063 output: 29 thoughts: 47 Thoughts: Here's my analysis of the provided text, rendered as a first-person expert summary: **Digging into the LiveUpdate Implementation** Okay, so I need to understand the role of `memfd_luo_preserve` or, more specifically, how `LIVEUPDATE_MEMFD` is being utilized within this system. My immediate focus is on tracing its usage – what functions call it, what are the implications of those calls? Are we dealing with file preservation across updates, or something more nuanced? My experience suggests there could be key performance or security considerations here, and the implementation details will dictate what those are. I also need to broaden the search. `liveupdate` is the obvious keyword, but I'll need to explore related terms. I should look for usages of functions like `liveupdate_register_file_handler`, which is a common pattern, and other functions associated with the general "live update" functionality. I'm thinking about things like in-place updates, rollback strategies, and the overall update lifecycle. The goal is to get a holistic picture of the live update process, and the specific use of the `LIVEUPDATE_MEMFD` in the architecture. |
| 8/2 | 2026/10/28 01:46 | tool | grepper |
0mArgs:{
"Expression": "liveupdate_file_handler|liveupdate_register_file_handler"
}Results: {
"Output": "include/linux/liveupdate.h-19-\ninclude/linux/liveupdate.h:20:struct liveupdate_file_handler;\ninclude/linux/liveupdate.h-21-struct liveupdate_flb;\n--\ninclude/linux/liveupdate.h=46=struct liveupdate_file_op_args {\ninclude/linux/liveupdate.h:47:\tstruct liveupdate_file_handler *handler;\ninclude/linux/liveupdate.h-48-\tint retrieve_status;\n--\ninclude/linux/liveupdate.h=74=struct liveupdate_file_ops {\ninclude/linux/liveupdate.h:75:\tbool (*can_preserve)(struct liveupdate_file_handler *handler,\ninclude/linux/liveupdate.h-76-\t\t\t struct file *file);\n--\ninclude/linux/liveupdate.h-88-/**\ninclude/linux/liveupdate.h:89: * struct liveupdate_file_handler - Represents a handler for a live-updatable file type.\ninclude/linux/liveupdate.h-90- * @ops: Callback functions\n--\ninclude/linux/liveupdate.h-100- */\ninclude/linux/liveupdate.h:101:struct liveupdate_file_handler {\ninclude/linux/liveupdate.h-102-\tconst struct liveupdate_file_ops *ops;\n--\ninclude/linux/liveupdate.h=234=int liveupdate_reboot(void);\ninclude/linux/liveupdate.h-235-\ninclude/linux/liveupdate.h:236:int liveupdate_register_file_handler(struct liveupdate_file_handler *fh);\ninclude/linux/liveupdate.h:237:void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh);\ninclude/linux/liveupdate.h-238-\ninclude/linux/liveupdate.h:239:int liveupdate_register_flb(struct liveupdate_file_handler *fh,\ninclude/linux/liveupdate.h-240-\t\t\t struct liveupdate_flb *flb);\ninclude/linux/liveupdate.h:241:void liveupdate_unregister_flb(struct liveupdate_file_handler *fh,\ninclude/linux/liveupdate.h-242-\t\t\t struct liveupdate_flb *flb);\n--\ninclude/linux/liveupdate.h=257=static inline int liveupdate_reboot(void)\n--\ninclude/linux/liveupdate.h-261-\ninclude/linux/liveupdate.h:262:static inline int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)\ninclude/linux/liveupdate.h-263-{\n--\ninclude/linux/liveupdate.h-266-\ninclude/linux/liveupdate.h:267:static inline void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)\ninclude/linux/liveupdate.h-268-{\n--\ninclude/linux/liveupdate.h-270-\ninclude/linux/liveupdate.h:271:static inline int liveupdate_register_flb(struct liveupdate_file_handler *fh,\ninclude/linux/liveupdate.h-272-\t\t\t\t\t struct liveupdate_flb *flb)\n--\ninclude/linux/liveupdate.h-276-\ninclude/linux/liveupdate.h:277:static inline void liveupdate_unregister_flb(struct liveupdate_file_handler *fh,\ninclude/linux/liveupdate.h-278-\t\t\t\t\t struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_file.c-20- * Kernel modules responsible for a specific file type (e.g., memfd, vfio)\nkernel/liveupdate/luo_file.c:21: * register a \u0026struct liveupdate_file_handler. This handler provides a set of\nkernel/liveupdate/luo_file.c-22- * callbacks that LUO invokes at different stages of the update process, most\n--\nkernel/liveupdate/luo_file.c=119=static DEFINE_XARRAY(luo_preserved_files);\n--\nkernel/liveupdate/luo_file.c-122- * struct luo_file - Represents a single preserved file instance.\nkernel/liveupdate/luo_file.c:123: * @fh: Pointer to the \u0026struct liveupdate_file_handler that manages\nkernel/liveupdate/luo_file.c-124- * this type of file.\n--\nkernel/liveupdate/luo_file.c=161=struct luo_file {\nkernel/liveupdate/luo_file.c:162:\tstruct liveupdate_file_handler *fh;\nkernel/liveupdate/luo_file.c-163-\tstruct file *file;\n--\nkernel/liveupdate/luo_file.c-171-\nkernel/liveupdate/luo_file.c:172:static unsigned long luo_get_id(struct liveupdate_file_handler *fh,\nkernel/liveupdate/luo_file.c-173-\t\t\t\tstruct file *file)\n--\nkernel/liveupdate/luo_file.c=230=int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)\n--\nkernel/liveupdate/luo_file.c-232-\tstruct liveupdate_file_op_args args = {0};\nkernel/liveupdate/luo_file.c:233:\tstruct liveupdate_file_handler *fh;\nkernel/liveupdate/luo_file.c-234-\tstruct luo_file *luo_file;\n--\nkernel/liveupdate/luo_file.c=719=static int luo_file_deserialize_one(struct luo_file_set *file_set,\n--\nkernel/liveupdate/luo_file.c-721-{\nkernel/liveupdate/luo_file.c:722:\tstruct liveupdate_file_handler *fh;\nkernel/liveupdate/luo_file.c-723-\tbool handler_found = false;\n--\nkernel/liveupdate/luo_file.c=855=void luo_file_set_destroy(struct luo_file_set *file_set)\n--\nkernel/liveupdate/luo_file.c-862-/**\nkernel/liveupdate/luo_file.c:863: * liveupdate_register_file_handler - Register a file handler with LUO.\nkernel/liveupdate/luo_file.c:864: * @fh: Pointer to a caller-allocated \u0026struct liveupdate_file_handler.\nkernel/liveupdate/luo_file.c-865- * The caller must initialize this structure, including a unique\n--\nkernel/liveupdate/luo_file.c-873- */\nkernel/liveupdate/luo_file.c:874:int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_file.c-875-{\nkernel/liveupdate/luo_file.c:876:\tstruct liveupdate_file_handler *fh_iter;\nkernel/liveupdate/luo_file.c-877-\tint err;\n--\nkernel/liveupdate/luo_file.c-917- * Unregisters the file handler from the liveupdate core. This function\nkernel/liveupdate/luo_file.c:918: * reverses the operations of liveupdate_register_file_handler().\nkernel/liveupdate/luo_file.c-919- */\nkernel/liveupdate/luo_file.c:920:void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_file.c-921-{\n--\nkernel/liveupdate/luo_flb.c=211=void liveupdate_flb_put_incoming(struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_flb.c-252- */\nkernel/liveupdate/luo_flb.c:253:int luo_flb_file_preserve(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_flb.c-254-{\n--\nkernel/liveupdate/luo_flb.c-288- */\nkernel/liveupdate/luo_flb.c:289:void luo_flb_file_unpreserve(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_flb.c-290-{\n--\nkernel/liveupdate/luo_flb.c-309- */\nkernel/liveupdate/luo_flb.c:310:void luo_flb_file_finish(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_flb.c-311-{\n--\nkernel/liveupdate/luo_flb.c-319-\nkernel/liveupdate/luo_flb.c:320:static void luo_flb_unregister_one(struct liveupdate_file_handler *fh,\nkernel/liveupdate/luo_flb.c-321-\t\t\t\t struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_flb.c-362- */\nkernel/liveupdate/luo_flb.c:363:void luo_flb_unregister_all(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_flb.c-364-{\n--\nkernel/liveupdate/luo_flb.c-397- */\nkernel/liveupdate/luo_flb.c:398:int liveupdate_register_flb(struct liveupdate_file_handler *fh,\nkernel/liveupdate/luo_flb.c-399-\t\t\t struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_flb.c-477- */\nkernel/liveupdate/luo_flb.c:478:void liveupdate_unregister_flb(struct liveupdate_file_handler *fh,\nkernel/liveupdate/luo_flb.c-479-\t\t\t struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_internal.h=99=void luo_file_set_destroy(struct luo_file_set *file_set);\nkernel/liveupdate/luo_internal.h-100-\nkernel/liveupdate/luo_internal.h:101:int luo_flb_file_preserve(struct liveupdate_file_handler *fh);\nkernel/liveupdate/luo_internal.h:102:void luo_flb_file_unpreserve(struct liveupdate_file_handler *fh);\nkernel/liveupdate/luo_internal.h:103:void luo_flb_file_finish(struct liveupdate_file_handler *fh);\nkernel/liveupdate/luo_internal.h:104:void luo_flb_unregister_all(struct liveupdate_file_handler *fh);\nkernel/liveupdate/luo_internal.h-105-int __init luo_flb_setup_outgoing(u64 *flbs_pa);\n--\nkernel/liveupdate/luo_internal.h=107=void luo_flb_serialize(void);\n--\nkernel/liveupdate/luo_internal.h-109-#ifdef CONFIG_LIVEUPDATE_TEST\nkernel/liveupdate/luo_internal.h:110:void liveupdate_test_register(struct liveupdate_file_handler *fh);\nkernel/liveupdate/luo_internal.h-111-#else\nkernel/liveupdate/luo_internal.h:112:static inline void liveupdate_test_register(struct liveupdate_file_handler *fh) { }\nkernel/liveupdate/luo_internal.h-113-#endif\n--\nlib/tests/liveupdate.c=87=static void liveupdate_test_init(void)\n--\nlib/tests/liveupdate.c-114-\nlib/tests/liveupdate.c:115:void liveupdate_test_register(struct liveupdate_file_handler *fh)\nlib/tests/liveupdate.c-116-{\n--\nmm/memfd_luo.c=573=static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)\n--\nmm/memfd_luo.c-634-\nmm/memfd_luo.c:635:static bool memfd_luo_can_preserve(struct liveupdate_file_handler *handler,\nmm/memfd_luo.c-636-\t\t\t\t struct file *file)\n--\nmm/memfd_luo.c=648=static const struct liveupdate_file_ops memfd_luo_file_ops = {\n--\nmm/memfd_luo.c-658-\nmm/memfd_luo.c:659:static struct liveupdate_file_handler memfd_luo_handler = {\nmm/memfd_luo.c-660-\t.ops = \u0026memfd_luo_file_ops,\n--\nmm/memfd_luo.c=664=static int __init memfd_luo_init(void)\nmm/memfd_luo.c-665-{\nmm/memfd_luo.c:666:\tint err = liveupdate_register_file_handler(\u0026memfd_luo_handler);\nmm/memfd_luo.c-667-\n"
} |
| 9/2 | 2026/10/28 01:46 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 23787 output: 44 thoughts: 38 Thoughts: Here's my analysis of the situation: **Investigating the User-Space Invocation of `luo_preserve_file`** Alright, let's get down to brass tacks. I need to understand how `luo_preserve_file` is being triggered from the user space. My initial instinct is to look for an `ioctl` call or perhaps a direct system call. These are the typical mechanisms for user-space interaction with kernel functionality. To pinpoint where to start looking, I'll zero in on the `kernel/liveupdate/` directory. That seems like the most logical location, given the function's name and probable function. Digging through there should give me the entry point and reveal the user-space interface. From there, I can trace the call chain if necessary. |
| 10/2 | 2026/10/28 01:46 | tool | grepper |
0mArgs:{
"Expression": "luo_preserve_file",
"PathPrefixes": [
"kernel/liveupdate/",
"include/uapi/linux/liveupdate"
]
}Results: {
"Output": "kernel/liveupdate/luo_file.c-46- * 1. Preserve (Normal Operation): A userspace agent preserves files one by one\nkernel/liveupdate/luo_file.c:47: * via an ioctl. For each file, luo_preserve_file() finds a compatible\nkernel/liveupdate/luo_file.c-48- * handler, calls its .preserve() operation, and creates an internal \u0026struct\n--\nkernel/liveupdate/luo_file.c=119=static DEFINE_XARRAY(luo_preserved_files);\n--\nkernel/liveupdate/luo_file.c-149- * This structure is the core in-kernel representation of a single file being\nkernel/liveupdate/luo_file.c:150: * managed through a live update. An instance is created by luo_preserve_file()\nkernel/liveupdate/luo_file.c-151- * to link a 'struct file' to its corresponding handler, a user-provided token,\n--\nkernel/liveupdate/luo_file.c=178=static bool luo_token_is_used(struct luo_file_set *file_set, u64 token)\n--\nkernel/liveupdate/luo_file.c-190-/**\nkernel/liveupdate/luo_file.c:191: * luo_preserve_file - Initiate the preservation of a file descriptor.\nkernel/liveupdate/luo_file.c-192- * @file_set: The file_set to which the preserved file will be added.\n--\nkernel/liveupdate/luo_file.c-229- */\nkernel/liveupdate/luo_file.c:230:int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)\nkernel/liveupdate/luo_file.c-231-{\n--\nkernel/liveupdate/luo_file.c-326- * 3. Releases the reference to the 'struct file' that was taken by\nkernel/liveupdate/luo_file.c:327: * luo_preserve_file() via fput(), returning ownership.\nkernel/liveupdate/luo_file.c-328- * 4. Frees the memory associated with the internal 'struct luo_file'.\n--\nkernel/liveupdate/luo_flb.c=211=void liveupdate_flb_put_incoming(struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_flb.c-249- *\nkernel/liveupdate/luo_flb.c:250: * Context: Called from luo_preserve_file()\nkernel/liveupdate/luo_flb.c-251- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_internal.h=85=int luo_session_deserialize(void);\nkernel/liveupdate/luo_internal.h-86-\nkernel/liveupdate/luo_internal.h:87:int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd);\nkernel/liveupdate/luo_internal.h-88-void luo_file_unpreserve_files(struct luo_file_set *file_set);\n--\nkernel/liveupdate/luo_session.c=263=static int luo_session_preserve_fd(struct luo_session *session,\n--\nkernel/liveupdate/luo_session.c-269-\tguard(mutex)(\u0026session-\u003emutex);\nkernel/liveupdate/luo_session.c:270:\terr = luo_preserve_file(\u0026session-\u003efile_set, argp-\u003etoken, argp-\u003efd);\nkernel/liveupdate/luo_session.c-271-\tif (err)\n"
} |
| 11/2 | 2026/10/28 01:46 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 24998 output: 34 thoughts: 76 Thoughts: Here's my take on those thoughts: **Analyzing the Liveupdate (KHO/LUO) User Interface** Alright, that's interesting. I'm seeing that Liveupdate, the Kexec Handover / Live Update Orchestrator (LUO), actually exposes a user-facing device or session. What's caught my attention is that userspace is making `ioctl` calls to preserve file descriptors, and that includes `memfd`! This has some serious implications for live updates and what can be updated. This suggests a very controlled and potentially powerful mechanism for how updates are handled. Now, I'm going to dig into `kernel/liveupdate/luo_session.c`. That's where the magic is. I need to understand exactly how this mechanism is presented to userspace. I want to see how this `ioctl` interface is designed, what specific controls are offered, and what protections, if any, are in place to prevent misuse. This could be a fascinating look at the architectural choices involved in designing a safe and efficient live update system. I'm looking for the details that will tell the story of the Kexec Handover process. |
| 12/2 | 2026/10/28 01:46 | tool | grepper |
0mArgs:{
"Expression": "file_operations|miscdevice|ioctl",
"PathPrefixes": [
"kernel/liveupdate/"
]
}Results: {
"Output": "kernel/liveupdate/luo_core.c-57-#include \u003clinux/liveupdate.h\u003e\nkernel/liveupdate/luo_core.c:58:#include \u003clinux/miscdevice.h\u003e\nkernel/liveupdate/luo_core.c-59-#include \u003clinux/mm.h\u003e\n--\nkernel/liveupdate/luo_core.c=244=bool liveupdate_enabled(void)\n--\nkernel/liveupdate/luo_core.c-249-/**\nkernel/liveupdate/luo_core.c:250: * DOC: LUO ioctl Interface\nkernel/liveupdate/luo_core.c-251- *\n--\nkernel/liveupdate/luo_core.c=265=struct luo_device_state {\nkernel/liveupdate/luo_core.c:266:\tstruct miscdevice miscdev;\nkernel/liveupdate/luo_core.c-267-\tatomic_t in_use;\n--\nkernel/liveupdate/luo_core.c-269-\nkernel/liveupdate/luo_core.c:270:static int luo_ioctl_create_session(struct luo_ucmd *ucmd)\nkernel/liveupdate/luo_core.c-271-{\nkernel/liveupdate/luo_core.c:272:\tstruct liveupdate_ioctl_create_session *argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-273-\tstruct file *file;\n--\nkernel/liveupdate/luo_core.c-299-\nkernel/liveupdate/luo_core.c:300:static int luo_ioctl_retrieve_session(struct luo_ucmd *ucmd)\nkernel/liveupdate/luo_core.c-301-{\nkernel/liveupdate/luo_core.c:302:\tstruct liveupdate_ioctl_retrieve_session *argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-303-\tstruct file *file;\n--\nkernel/liveupdate/luo_core.c=358=union ucmd_buffer {\nkernel/liveupdate/luo_core.c:359:\tstruct liveupdate_ioctl_create_session create;\nkernel/liveupdate/luo_core.c:360:\tstruct liveupdate_ioctl_retrieve_session retrieve;\nkernel/liveupdate/luo_core.c-361-};\nkernel/liveupdate/luo_core.c-362-\nkernel/liveupdate/luo_core.c:363:struct luo_ioctl_op {\nkernel/liveupdate/luo_core.c-364-\tunsigned int size;\nkernel/liveupdate/luo_core.c-365-\tunsigned int min_size;\nkernel/liveupdate/luo_core.c:366:\tunsigned int ioctl_num;\nkernel/liveupdate/luo_core.c-367-\tint (*execute)(struct luo_ucmd *ucmd);\n--\nkernel/liveupdate/luo_core.c-369-\nkernel/liveupdate/luo_core.c:370:#define IOCTL_OP(_ioctl, _fn, _struct, _last) \\\nkernel/liveupdate/luo_core.c:371:\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_BASE] = { \\\nkernel/liveupdate/luo_core.c-372-\t\t.size = sizeof(_struct) + \\\n--\nkernel/liveupdate/luo_core.c-375-\t\t.min_size = offsetofend(_struct, _last), \\\nkernel/liveupdate/luo_core.c:376:\t\t.ioctl_num = _ioctl, \\\nkernel/liveupdate/luo_core.c-377-\t\t.execute = _fn, \\\n--\nkernel/liveupdate/luo_core.c-379-\nkernel/liveupdate/luo_core.c:380:static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c:381:\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c:382:\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c:383:\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c:384:\t\t struct liveupdate_ioctl_retrieve_session, name),\nkernel/liveupdate/luo_core.c-385-};\nkernel/liveupdate/luo_core.c-386-\nkernel/liveupdate/luo_core.c:387:static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)\nkernel/liveupdate/luo_core.c-388-{\nkernel/liveupdate/luo_core.c:389:\tconst struct luo_ioctl_op *op;\nkernel/liveupdate/luo_core.c-390-\tstruct luo_ucmd ucmd = {};\n--\nkernel/liveupdate/luo_core.c-395-\tnr = _IOC_NR(cmd);\nkernel/liveupdate/luo_core.c:396:\tif (nr - LIVEUPDATE_CMD_BASE \u003e= ARRAY_SIZE(luo_ioctl_ops))\nkernel/liveupdate/luo_core.c-397-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_core.c-403-\nkernel/liveupdate/luo_core.c:404:\top = \u0026luo_ioctl_ops[nr - LIVEUPDATE_CMD_BASE];\nkernel/liveupdate/luo_core.c:405:\tif (op-\u003eioctl_num != cmd)\nkernel/liveupdate/luo_core.c-406-\t\treturn -ENOIOCTLCMD;\n--\nkernel/liveupdate/luo_core.c-418-\nkernel/liveupdate/luo_core.c:419:static const struct file_operations luo_fops = {\nkernel/liveupdate/luo_core.c-420-\t.owner\t\t= THIS_MODULE,\n--\nkernel/liveupdate/luo_core.c-422-\t.release\t= luo_release,\nkernel/liveupdate/luo_core.c:423:\t.unlocked_ioctl\t= luo_ioctl,\nkernel/liveupdate/luo_core.c-424-};\n--\nkernel/liveupdate/luo_core.c=426=static struct luo_device_state luo_dev = {\n--\nkernel/liveupdate/luo_core.c-434-\nkernel/liveupdate/luo_core.c:435:static int __init liveupdate_ioctl_init(void)\nkernel/liveupdate/luo_core.c-436-{\n--\nkernel/liveupdate/luo_core.c-441-}\nkernel/liveupdate/luo_core.c:442:late_initcall(liveupdate_ioctl_init);\n--\nkernel/liveupdate/luo_file.c-46- * 1. Preserve (Normal Operation): A userspace agent preserves files one by one\nkernel/liveupdate/luo_file.c:47: * via an ioctl. For each file, luo_preserve_file() finds a compatible\nkernel/liveupdate/luo_file.c-48- * handler, calls its .preserve() operation, and creates an internal \u0026struct\n--\nkernel/liveupdate/luo_file.c=178=static bool luo_token_is_used(struct luo_file_set *file_set, u64 token)\n--\nkernel/liveupdate/luo_file.c-219- *\nkernel/liveupdate/luo_file.c:220: * Context: Can be called from an ioctl handler during normal system operation.\nkernel/liveupdate/luo_file.c-221- * Return: 0 on success. Returns a negative errno on failure:\n--\nkernel/liveupdate/luo_file.c=517=void luo_file_unfreeze(struct luo_file_set *file_set,\n--\nkernel/liveupdate/luo_file.c-545- *\nkernel/liveupdate/luo_file.c:546: * Context: Can be called from an ioctl or other in-kernel code in the new\nkernel/liveupdate/luo_file.c-547- * kernel.\n--\nkernel/liveupdate/luo_file.c=632=static void luo_file_finish_one(struct luo_file_set *file_set,\n--\nkernel/liveupdate/luo_file.c-676- *\nkernel/liveupdate/luo_file.c:677: * Context: Can be called from an ioctl handler in the new kernel.\nkernel/liveupdate/luo_file.c-678- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_session.c-23- * - Userspace Interface: Session management is driven from userspace via\nkernel/liveupdate/luo_session.c:24: * ioctls on /dev/liveupdate.\nkernel/liveupdate/luo_session.c-25- *\n--\nkernel/liveupdate/luo_session.c-56- * 1. `luo_session_serialize_rwsem` (global rwsem):\nkernel/liveupdate/luo_session.c:57: * Protects session mutations (creation, retrieval, release, and ioctls)\nkernel/liveupdate/luo_session.c-58- * against the serialization process during reboot.\n--\nkernel/liveupdate/luo_session.c-61- * `luo_session_create()`, `luo_session_retrieve()`, `luo_session_release()`,\nkernel/liveupdate/luo_session.c:62: * and `luo_session_ioctl()`).\nkernel/liveupdate/luo_session.c-63- * - Writer: Taken by the serialization process (`luo_session_serialize()`)\n--\nkernel/liveupdate/luo_session.c=343=union ucmd_buffer {\n--\nkernel/liveupdate/luo_session.c-349-\nkernel/liveupdate/luo_session.c:350:/* Type of sessions the ioctl applies to. */\nkernel/liveupdate/luo_session.c:351:enum luo_ioctl_type {\nkernel/liveupdate/luo_session.c-352-\tLUO_IOCTL_INCOMING,\n--\nkernel/liveupdate/luo_session.c-356-\nkernel/liveupdate/luo_session.c:357:struct luo_ioctl_op {\nkernel/liveupdate/luo_session.c-358-\tunsigned int size;\nkernel/liveupdate/luo_session.c-359-\tunsigned int min_size;\nkernel/liveupdate/luo_session.c:360:\tunsigned int ioctl_num;\nkernel/liveupdate/luo_session.c:361:\tenum luo_ioctl_type type;\nkernel/liveupdate/luo_session.c-362-\tint (*execute)(struct luo_session *session, struct luo_ucmd *ucmd);\n--\nkernel/liveupdate/luo_session.c-364-\nkernel/liveupdate/luo_session.c:365:#define IOCTL_OP(_ioctl, _fn, _struct, _last, _type) \\\nkernel/liveupdate/luo_session.c:366:\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_SESSION_BASE] = { \\\nkernel/liveupdate/luo_session.c-367-\t\t.size = sizeof(_struct) + \\\n--\nkernel/liveupdate/luo_session.c-370-\t\t.min_size = offsetofend(_struct, _last), \\\nkernel/liveupdate/luo_session.c:371:\t\t.ioctl_num = _ioctl, \\\nkernel/liveupdate/luo_session.c-372-\t\t.type = _type, \\\n--\nkernel/liveupdate/luo_session.c-375-\nkernel/liveupdate/luo_session.c:376:static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c-377-\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\n--\nkernel/liveupdate/luo_session.c-386-\nkernel/liveupdate/luo_session.c:387:static bool luo_ioctl_type_valid(struct luo_session *session,\nkernel/liveupdate/luo_session.c:388:\t\t\t\t const struct luo_ioctl_op *op)\nkernel/liveupdate/luo_session.c-389-{\n--\nkernel/liveupdate/luo_session.c-403-\nkernel/liveupdate/luo_session.c:404:static long luo_session_ioctl(struct file *filep, unsigned int cmd,\nkernel/liveupdate/luo_session.c-405-\t\t\t unsigned long arg)\n--\nkernel/liveupdate/luo_session.c-407-\tstruct luo_session *session = filep-\u003eprivate_data;\nkernel/liveupdate/luo_session.c:408:\tconst struct luo_ioctl_op *op;\nkernel/liveupdate/luo_session.c-409-\tstruct luo_ucmd ucmd = {};\n--\nkernel/liveupdate/luo_session.c-415-\tif (nr \u003c LIVEUPDATE_CMD_SESSION_BASE || (nr - LIVEUPDATE_CMD_SESSION_BASE) \u003e=\nkernel/liveupdate/luo_session.c:416:\t ARRAY_SIZE(luo_session_ioctl_ops)) {\nkernel/liveupdate/luo_session.c-417-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_session.c-424-\nkernel/liveupdate/luo_session.c:425:\top = \u0026luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];\nkernel/liveupdate/luo_session.c:426:\tif (op-\u003eioctl_num != cmd)\nkernel/liveupdate/luo_session.c-427-\t\treturn -ENOIOCTLCMD;\nkernel/liveupdate/luo_session.c:428:\tif (!luo_ioctl_type_valid(session, op))\nkernel/liveupdate/luo_session.c-429-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_session.c-442-\nkernel/liveupdate/luo_session.c:443:static const struct file_operations luo_session_fops = {\nkernel/liveupdate/luo_session.c-444-\t.owner = THIS_MODULE,\nkernel/liveupdate/luo_session.c-445-\t.release = luo_session_release,\nkernel/liveupdate/luo_session.c:446:\t.unlocked_ioctl = luo_session_ioctl,\nkernel/liveupdate/luo_session.c-447-};\n"
} |
| 13/2 | 2026/10/28 01:46 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 29256 output: 37 thoughts: 23 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving into /dev/liveupdate** Right, `/dev/liveupdate`... that's a *miscdevice*, a familiar starting point. My first instinct is always to understand its configuration options. I need to quickly establish the relevant Kconfig symbols to pinpoint how this functionality is enabled, disabled, and customized. Time to dig into the kernel configuration files and build dependencies. Let's see what’s controlling its behavior and how deeply it's woven into the larger system. |
| 14/2 | 2026/10/28 01:46 | tool | grepper |
0mArgs:{
"Expression": "LIVEUPDATE",
"PathPrefixes": [
"init/Kconfig",
"mm/",
"kernel/"
]
}Results: {
"Output": "kernel/liveupdate/Kconfig=38=config KEXEC_HANDOVER_ENABLE_DEFAULT\n--\nkernel/liveupdate/Kconfig-51-\nkernel/liveupdate/Kconfig:52:config LIVEUPDATE\nkernel/liveupdate/Kconfig-53-\tbool \"Live Update Orchestrator\"\n--\nkernel/liveupdate/Kconfig-72-\nkernel/liveupdate/Kconfig:73:config LIVEUPDATE_MEMFD\nkernel/liveupdate/Kconfig-74-\tbool \"Live update support for memfd\"\nkernel/liveupdate/Kconfig:75:\tdepends on LIVEUPDATE\nkernel/liveupdate/Kconfig-76-\tdepends on MEMFD_CREATE\nkernel/liveupdate/Kconfig-77-\tdepends on SHMEM\nkernel/liveupdate/Kconfig:78:\tdefault LIVEUPDATE\nkernel/liveupdate/Kconfig-79-\thelp\n--\nkernel/liveupdate/Makefile=11=obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS)\t+= kexec_handover_debugfs.o\nkernel/liveupdate/Makefile-12-\nkernel/liveupdate/Makefile:13:obj-$(CONFIG_LIVEUPDATE)\t\t+= luo.o\n--\nkernel/liveupdate/luo_core.c=363=struct luo_ioctl_op {\n--\nkernel/liveupdate/luo_core.c-370-#define IOCTL_OP(_ioctl, _fn, _struct, _last) \\\nkernel/liveupdate/luo_core.c:371:\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_BASE] = { \\\nkernel/liveupdate/luo_core.c-372-\t\t.size = sizeof(_struct) + \\\n--\nkernel/liveupdate/luo_core.c=380=static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c:381:\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c-382-\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c:383:\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c-384-\t\t struct liveupdate_ioctl_retrieve_session, name),\n--\nkernel/liveupdate/luo_core.c=387=static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)\n--\nkernel/liveupdate/luo_core.c-395-\tnr = _IOC_NR(cmd);\nkernel/liveupdate/luo_core.c:396:\tif (nr - LIVEUPDATE_CMD_BASE \u003e= ARRAY_SIZE(luo_ioctl_ops))\nkernel/liveupdate/luo_core.c-397-\t\treturn -EINVAL;\n--\nkernel/liveupdate/luo_core.c-403-\nkernel/liveupdate/luo_core.c:404:\top = \u0026luo_ioctl_ops[nr - LIVEUPDATE_CMD_BASE];\nkernel/liveupdate/luo_core.c-405-\tif (op-\u003eioctl_num != cmd)\n--\nkernel/liveupdate/luo_internal.h=70=struct luo_session {\nkernel/liveupdate/luo_internal.h:71:\tchar name[LIVEUPDATE_SESSION_NAME_LENGTH];\nkernel/liveupdate/luo_internal.h-72-\tstruct list_head list;\n--\nkernel/liveupdate/luo_internal.h=107=void luo_flb_serialize(void);\nkernel/liveupdate/luo_internal.h-108-\nkernel/liveupdate/luo_internal.h:109:#ifdef CONFIG_LIVEUPDATE_TEST\nkernel/liveupdate/luo_internal.h-110-void liveupdate_test_register(struct liveupdate_file_handler *fh);\n--\nkernel/liveupdate/luo_session.c=357=struct luo_ioctl_op {\n--\nkernel/liveupdate/luo_session.c-365-#define IOCTL_OP(_ioctl, _fn, _struct, _last, _type) \\\nkernel/liveupdate/luo_session.c:366:\t[_IOC_NR(_ioctl) - LIVEUPDATE_CMD_SESSION_BASE] = { \\\nkernel/liveupdate/luo_session.c-367-\t\t.size = sizeof(_struct) + \\\n--\nkernel/liveupdate/luo_session.c=376=static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c:377:\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\nkernel/liveupdate/luo_session.c-378-\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:379:\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\nkernel/liveupdate/luo_session.c-380-\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\nkernel/liveupdate/luo_session.c:381:\tIOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,\nkernel/liveupdate/luo_session.c-382-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:383:\tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\nkernel/liveupdate/luo_session.c-384-\t\t struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),\n--\nkernel/liveupdate/luo_session.c=404=static long luo_session_ioctl(struct file *filep, unsigned int cmd,\n--\nkernel/liveupdate/luo_session.c-414-\tnr = _IOC_NR(cmd);\nkernel/liveupdate/luo_session.c:415:\tif (nr \u003c LIVEUPDATE_CMD_SESSION_BASE || (nr - LIVEUPDATE_CMD_SESSION_BASE) \u003e=\nkernel/liveupdate/luo_session.c-416-\t ARRAY_SIZE(luo_session_ioctl_ops)) {\n--\nkernel/liveupdate/luo_session.c-424-\nkernel/liveupdate/luo_session.c:425:\top = \u0026luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];\nkernel/liveupdate/luo_session.c-426-\tif (op-\u003eioctl_num != cmd)\n--\nkernel/liveupdate/luo_session.c=466=int luo_session_create(const char *name, struct file **filep)\nkernel/liveupdate/luo_session.c-467-{\nkernel/liveupdate/luo_session.c:468:\tsize_t len = strnlen(name, LIVEUPDATE_SESSION_NAME_LENGTH);\nkernel/liveupdate/luo_session.c-469-\tstruct luo_session *session;\n--\nkernel/liveupdate/luo_session.c-471-\nkernel/liveupdate/luo_session.c:472:\tif (len == 0 || len \u003e LIVEUPDATE_SESSION_NAME_LENGTH - 1)\nkernel/liveupdate/luo_session.c-473-\t\treturn -EINVAL;\n--\nmm/Makefile=103=obj-$(CONFIG_PAGE_COUNTER) += page_counter.o\nmm/Makefile:104:obj-$(CONFIG_LIVEUPDATE_MEMFD) += memfd_luo.o\nmm/Makefile-105-obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o\n"
} |
| 15/2 | 2026/10/28 01:46 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 31451 output: 33 thoughts: 17 Thoughts: Here's a first-person summary, tailored for an expert audience, based on the prompt: **Analyzing `CONFIG_LIVEUPDATE` Dependencies and Kconfig Configuration** Okay, let's dive into this. My immediate thought is, before I start down any development or debugging path, I need to thoroughly understand the Kconfig implications and any dependencies for `CONFIG_LIVEUPDATE`. I'm going to have to carefully examine the Kconfig files, starting with the core ones and tracing any relevant includes or source file dependencies. I need to quickly identify not just the obvious dependencies like the core kernel features that `LIVEUPDATE` hooks into, but also any subtle interactions with other configurations that might seem unrelated at first glance, but will impact live updates. I know from experience that hidden dependencies are the bane of this type of work, so I'll be thorough. I'll be making note of any conditional builds that might be triggered, any hardware platforms affected, and any interactions with security features. Effectively, I am setting the stage for success. |
| 16/2 | 2026/10/28 01:47 | tool | grepper |
0mArgs:{
"Expression": "config LIVEUPDATE\\b",
"PathPrefixes": [
"kernel/liveupdate/Kconfig"
]
}Results: {
"Output": "kernel/liveupdate/Kconfig=38=config KEXEC_HANDOVER_ENABLE_DEFAULT\n--\nkernel/liveupdate/Kconfig-51-\nkernel/liveupdate/Kconfig:52:config LIVEUPDATE\nkernel/liveupdate/Kconfig-53-\tbool \"Live Update Orchestrator\"\n"
} |
| 17/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 31799 output: 34 thoughts: 19 Thoughts: Here's a summary of my thought process, keeping in mind my expert understanding: **Analyzing Kernel Liveupdate Configuration** Okay, let's dive in. I need to understand the configuration options for the live update functionality in the kernel. The obvious place to start is the `Kconfig` file, specifically around line 50. I'm guessing that area will likely contain the core settings or maybe even the initial definitions for this module. My experience tells me that `Kconfig` files are usually structured logically, with related options grouped together. I'm expecting to see dependencies, default values, help text, and likely some conditional compilation logic defined there. I'll be looking for clues about the scope of the live update features – whether they support different update mechanisms, different target hardware, different update methodologies, and what aspects the users are allowed to configure. I'll need to keep an eye out for potential conflicts or interactions with other kernel subsystems as well. My goal is to grasp the foundational configuration landscape of this live update mechanism so I can better understand its capabilities. |
| 18/2 | 2026/10/28 01:47 | tool | read-file |
0mArgs:{
"File": "kernel/liveupdate/Kconfig",
"FirstLine": 40,
"LineCount": 50
}Results: {
"Contents": " 40:\t\tdepends on KEXEC_HANDOVER\n 41:\t\thelp\n 42:\t\t Enable Kexec Handover by default. This avoids the need to\n 43:\t\t explicitly pass 'kho=on' on the kernel command line.\n 44:\t\n 45:\t\t This is useful for systems where KHO is a prerequisite for other\n 46:\t\t features, such as Live Update, ensuring the mechanism is always\n 47:\t\t active.\n 48:\t\n 49:\t\t The default behavior can still be overridden at boot time by\n 50:\t\t passing 'kho=off'.\n 51:\t\n 52:\tconfig LIVEUPDATE\n 53:\t\tbool \"Live Update Orchestrator\"\n 54:\t\tdepends on KEXEC_HANDOVER\n 55:\t\thelp\n 56:\t\t Enable the Live Update Orchestrator. Live Update is a mechanism,\n 57:\t\t typically based on kexec, that allows the kernel to be updated\n 58:\t\t while keeping selected devices operational across the transition.\n 59:\t\t These devices are intended to be reclaimed by the new kernel and\n 60:\t\t re-attached to their original workload without requiring a device\n 61:\t\t reset.\n 62:\t\n 63:\t\t Ability to handover a device from current to the next kernel depends\n 64:\t\t on specific support within device drivers and related kernel\n 65:\t\t subsystems.\n 66:\t\n 67:\t\t This feature primarily targets virtual machine hosts to quickly update\n 68:\t\t the kernel hypervisor with minimal disruption to the running virtual\n 69:\t\t machines.\n 70:\t\n 71:\t\t If unsure, say N.\n 72:\t\n 73:\tconfig LIVEUPDATE_MEMFD\n 74:\t\tbool \"Live update support for memfd\"\n 75:\t\tdepends on LIVEUPDATE\n 76:\t\tdepends on MEMFD_CREATE\n 77:\t\tdepends on SHMEM\n 78:\t\tdefault LIVEUPDATE\n 79:\t\thelp\n 80:\t\t Enable live update support for memfd regions. This allows preserving\n 81:\t\t memfd-backed memory across kernel live updates.\n 82:\t\n 83:\t\t This can be used to back VM memory with memfds, allowing the guest\n 84:\t\t memory to persist, or for other user workloads needing to preserve\n 85:\t\t pages.\n 86:\t\n 87:\t\t If unsure, say N.\n 88:\t\n 89:\tendmenu\n"
} |
| 19/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 32716 output: 48 thoughts: 13 Thoughts: Okay, let's dive into this. Here's my thought process on determining the dependencies of `KEXEC_HANDOVER`: **Unpacking KEXEC_HANDOVER Dependencies** Alright, I need to understand what this `KEXEC_HANDOVER` thing hinges upon. What other components or configurations does it rely on to function correctly? This isn't a complex debugging task; I just need to get the mental map right, understand the supporting pieces of this functionality, so I can predict likely areas for future investigation, or modification. |
| 20/2 | 2026/10/28 01:47 | tool | grepper |
0mArgs:{
"Expression": "config KEXEC_HANDOVER\\b",
"PathPrefixes": [
"kernel/liveupdate/Kconfig",
"kernel/Kconfig",
"arch/"
]
}Results: {
"Output": "kernel/liveupdate/Kconfig=3=menu \"Live Update and Kexec HandOver\"\nkernel/liveupdate/Kconfig-4-\nkernel/liveupdate/Kconfig:5:config KEXEC_HANDOVER\nkernel/liveupdate/Kconfig-6-\tbool \"kexec handover\"\n"
} |
| 21/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 32968 output: 33 thoughts: 21 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: **Analyzing Kernel Liveupdate Configuration** Okay, let's dive into this. My initial focus is the `kernel/liveupdate/Kconfig` file, specifically lines 1 through 40. I need to quickly grasp the foundational configuration options and dependencies related to the live update mechanism. I'm expecting to see the core features defined – whether it's related to the *basic framework*, *specific CPU architectures*, or *support for different update methods*. I'll be looking for the `config` symbols, any `depends on` statements that might give me insight into the prerequisites, and `select` directives that illuminate how these options interact and impact each other. I'll likely mentally categorize any `help` text provided, quickly assessing its level of detail and if it provides any architectural insights, or simply basic usage information. My goal at this stage isn't to build a comprehensive understanding, but to quickly map out the high-level configuration landscape. I'm expecting to be able to extrapolate some critical parameters, potentially relevant to the system being considered. |
| 22/2 | 2026/10/28 01:47 | tool | read-file |
0mArgs:{
"File": "kernel/liveupdate/Kconfig",
"FirstLine": 1,
"LineCount": 40
}Results: {
"Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\t\n 3:\tmenu \"Live Update and Kexec HandOver\"\n 4:\t\n 5:\tconfig KEXEC_HANDOVER\n 6:\t\tbool \"kexec handover\"\n 7:\t\tdepends on ARCH_SUPPORTS_KEXEC_HANDOVER \u0026\u0026 ARCH_SUPPORTS_KEXEC_FILE\n 8:\t\tselect MEMBLOCK_KHO_SCRATCH\n 9:\t\tselect KEXEC_FILE\n 10:\t\tselect LIBFDT\n 11:\t\tselect CMA\n 12:\t\thelp\n 13:\t\t Allow kexec to hand over state across kernels by generating and\n 14:\t\t passing additional metadata to the target kernel. This is useful\n 15:\t\t to keep data or state alive across the kexec. For this to work,\n 16:\t\t both source and target kernels need to have this option enabled.\n 17:\t\n 18:\tconfig KEXEC_HANDOVER_DEBUG\n 19:\t\tbool \"Enable Kexec Handover debug checks\"\n 20:\t\tdepends on KEXEC_HANDOVER\n 21:\t\thelp\n 22:\t\t This option enables extra sanity checks for the Kexec Handover\n 23:\t\t subsystem. Since, KHO performance is crucial in live update\n 24:\t\t scenarios and the extra code might be adding overhead it is\n 25:\t\t only optionally enabled.\n 26:\t\n 27:\tconfig KEXEC_HANDOVER_DEBUGFS\n 28:\t\tbool \"kexec handover debugfs interface\"\n 29:\t\tdefault KEXEC_HANDOVER\n 30:\t\tdepends on KEXEC_HANDOVER\n 31:\t\tselect DEBUG_FS\n 32:\t\thelp\n 33:\t\t Allow to control kexec handover device tree via debugfs\n 34:\t\t interface, i.e. finalize the state or aborting the finalization.\n 35:\t\t Also, enables inspecting the KHO fdt trees with the debugfs binary\n 36:\t\t blobs.\n 37:\t\n 38:\tconfig KEXEC_HANDOVER_ENABLE_DEFAULT\n 39:\t\tbool \"Enable kexec handover by default\"\n 40:\t\tdepends on KEXEC_HANDOVER\n"
} |
| 23/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 33818 output: 24 thoughts: 19 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and rendered in the first person: **Delving into the KEXEC Handover Support** Alright, let's dive in. I need to understand what exactly the `ARCH_SUPPORTS_KEXEC_HANDOVER` preprocessor symbol signifies within this context. I immediately recognize the term "KEXEC," indicating a kernel loading mechanism, but I'm going to need to remind myself of the specific nuances of a "handover" in this architecture. My mental model is pulling up the broader implications – potential support for things like kexec's ability to cleanly transition between kernels for live patching, crash dumps, or even rapid system upgrades. Is this a feature specific to this architecture? Does this flag indicate the ability to hand off control efficiently? I need to know the supported features. Let's see... |
| 24/2 | 2026/10/28 01:47 | tool | grepper |
0mArgs:{
"Expression": "ARCH_SUPPORTS_KEXEC_HANDOVER"
}Results: {
"Output": "arch/arm64/Kconfig=1706=config ARCH_DEFAULT_KEXEC_IMAGE_VERIFY_SIG\n--\narch/arm64/Kconfig-1708-\narch/arm64/Kconfig:1709:config ARCH_SUPPORTS_KEXEC_HANDOVER\narch/arm64/Kconfig-1710-\tdef_bool y\n--\narch/x86/Kconfig=1974=config ARCH_SUPPORTS_KEXEC_JUMP\n--\narch/x86/Kconfig-1976-\narch/x86/Kconfig:1977:config ARCH_SUPPORTS_KEXEC_HANDOVER\narch/x86/Kconfig-1978-\tdef_bool X86_64\n--\nkernel/liveupdate/Kconfig=5=config KEXEC_HANDOVER\nkernel/liveupdate/Kconfig-6-\tbool \"kexec handover\"\nkernel/liveupdate/Kconfig:7:\tdepends on ARCH_SUPPORTS_KEXEC_HANDOVER \u0026\u0026 ARCH_SUPPORTS_KEXEC_FILE\nkernel/liveupdate/Kconfig-8-\tselect MEMBLOCK_KHO_SCRATCH\n"
} |
| 25/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 34338 output: 34 thoughts: 1930 Thoughts: **Analyzing the Implications of Frozen Mappings in the Linux Kernel** Okay, so x86_64 supports this new feature. Now, let's dive deep into this patch. I need to understand exactly what changes it makes and, crucially, the *why* behind them. I see a lot of modifications related to a concept called "frozen mappings" – that's the key. First off, in `fs/inode.c`, that `WARN_ON_ONCE` in `evict()` is immediately grabbing my attention. Whenever an inode is evicted, it's called, so if `mapping_frozen` is true, we have a potentially serious problem! The comment suggests this should *never* happen, which makes that assertion even more critical. I need to keep this `WARN_ON_ONCE` in mind. New runtime checks? Gotta fuzz! The `include/linux/pagemap.h` file introduces the `AS_FROZEN` flag and associated inline functions for setting, clearing, and checking it. Pretty straightforward so far – this is the core mechanism. The removal of `SHMEM_F_MAPPING_FROZEN` and `shmem_freeze` from `include/linux/shmem_fs.h` is interesting too – this feature is no longer used by shmem, which tells me it's probably being refactored or superseded by these more general flags. Now, things get more interesting in `mm/filemap.c`. There are multiple `VM_WARN_ON_ONCE_FOLIO` calls when a mapping is frozen and the code hits a `page_cache_delete` or `__filemap_add_folio`. This means that if `mapping_frozen` is set, the code will trigger a warning. There are a lot of implications here. In `mm/huge_memory.c`, functions like `folio_check_splittable()` and `__folio_freeze_split_file()` are now explicitly checking for frozen mappings and returning `-EBUSY` if they're present. This suggests these mappings are related to huge pages and splitting operations. Similar checks and `-EBUSY` returns appear in `mm/khugepaged.c` during `collapse_file()` and in `mm/migrate.c` during folio migration, further solidifying the connection to memory management and migration logic. `mm/memfd_luo.c` looks like it's a major player. This seems to be a complete rewrite, introducing functions like `memfd_luo_preserve` and `memfd_luo_unpreserve`. It's using the new `mapping_set_frozen()` and `mapping_clear_frozen()` functions. The replacement of `memfd_pin_folios()` with a loop is a significant change, and I need to carefully analyze the implications for folio migration and preservation. I need to understand what `memfd_luo_preserve` does in order to truly understand the scope of the change. `mm/shmem.c` has a large number of changes, all revolving around checks for frozen mappings during operations like adding to the page cache, truncating, writing out, swapping in, and allocating. These all check and fail with `-EBUSY` if the mapping is frozen. The changes indicate that frozen mappings are *incompatible* with these shmem-specific operations, probably because they could lead to data corruption or inconsistency if performed on a "frozen" part of memory. Finally, `mm/truncate.c` has similar checks in `truncate_inode_folio()`, `truncate_inode_pages_range()`, and `folio_unmap_invalidate()`, all returning `-EBUSY` or simply returning if frozen, further confirming this restriction. `__remove_mapping` also checks if a mapping is frozen before removing folios. Truncation, unmapping, and removing folios are all operations that can change the state of the memory map. Alright, so the pattern is clear: a "frozen" mapping implies that *no* modification of folios or their mappings is allowed. Any operation that could alter the folio set or its association with the address space is blocked and will return a `-EBUSY` error, trigger a warning, or simply return. This includes splitting, collapsing, migrating, truncating, swapping, and adding. This is a serious constraint. Now, I need to know how these mappings get frozen, and under what circumstances a user would be able to trigger this. I need to understand the control flow into `memfd_luo_preserve()`. Is there a userland interface that enables this? I'm going to look into `/dev/liveupdate`. Time to check `kernel/liveupdate/luo_core.c`! |
| 26/2 | 2026/10/28 01:47 | tool | grepper |
0mArgs:{
"Expression": "liveupdate",
"PathPrefixes": [
"kernel/liveupdate/luo_core.c"
]
}Results: {
"Output": "kernel/liveupdate/luo_core.c-40- * .. note::\nkernel/liveupdate/luo_core.c:41: * To enable LUO, boot the kernel with the ``liveupdate=on`` command line\nkernel/liveupdate/luo_core.c-42- * parameter.\n--\nkernel/liveupdate/luo_core.c-56-#include \u003clinux/kobject.h\u003e\nkernel/liveupdate/luo_core.c:57:#include \u003clinux/liveupdate.h\u003e\nkernel/liveupdate/luo_core.c-58-#include \u003clinux/miscdevice.h\u003e\n--\nkernel/liveupdate/luo_core.c=67=static struct {\n--\nkernel/liveupdate/luo_core.c-69-\tstruct luo_ser *luo_ser_out;\nkernel/liveupdate/luo_core.c:70:\tu64 liveupdate_num;\nkernel/liveupdate/luo_core.c-71-} luo_global;\n--\nkernel/liveupdate/luo_core.c=76=DECLARE_RWSEM(luo_register_rwlock);\nkernel/liveupdate/luo_core.c-77-\nkernel/liveupdate/luo_core.c:78:static int __init early_liveupdate_param(char *buf)\nkernel/liveupdate/luo_core.c-79-{\n--\nkernel/liveupdate/luo_core.c-81-}\nkernel/liveupdate/luo_core.c:82:early_param(\"liveupdate\", early_liveupdate_param);\nkernel/liveupdate/luo_core.c-83-\nkernel/liveupdate/luo_core.c=84=static int __init luo_early_startup(void)\n--\nkernel/liveupdate/luo_core.c-91-\tif (!kho_is_enabled()) {\nkernel/liveupdate/luo_core.c:92:\t\tif (liveupdate_enabled())\nkernel/liveupdate/luo_core.c:93:\t\t\tpr_warn(\"Disabling liveupdate because KHO is disabled\\n\");\nkernel/liveupdate/luo_core.c-94-\t\tluo_global.enabled = false;\n--\nkernel/liveupdate/luo_core.c-120-\nkernel/liveupdate/luo_core.c:121:\tluo_global.liveupdate_num = luo_ser-\u003eliveupdate_num;\nkernel/liveupdate/luo_core.c:122:\tpr_info(\"Retrieved live update data, liveupdate number: %lld\\n\",\nkernel/liveupdate/luo_core.c:123:\t\tluo_global.liveupdate_num);\nkernel/liveupdate/luo_core.c-124-\n--\nkernel/liveupdate/luo_core.c-137-\nkernel/liveupdate/luo_core.c:138:static int __init liveupdate_early_init(void)\nkernel/liveupdate/luo_core.c-139-{\n--\nkernel/liveupdate/luo_core.c-150-}\nkernel/liveupdate/luo_core.c:151:early_initcall(liveupdate_early_init);\nkernel/liveupdate/luo_core.c-152-\n--\nkernel/liveupdate/luo_core.c=154=static int __init luo_state_setup(void)\n--\nkernel/liveupdate/luo_core.c-165-\tstrscpy(luo_ser-\u003ecompatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser-\u003ecompatible));\nkernel/liveupdate/luo_core.c:166:\tluo_ser-\u003eliveupdate_num = luo_global.liveupdate_num + 1;\nkernel/liveupdate/luo_core.c-167-\n--\nkernel/liveupdate/luo_core.c-190- * late initcall because it initializes the outgoing tree that is needed only\nkernel/liveupdate/luo_core.c:191: * once userspace starts using /dev/liveupdate.\nkernel/liveupdate/luo_core.c-192- */\nkernel/liveupdate/luo_core.c=193=static int __init luo_late_startup(void)\n--\nkernel/liveupdate/luo_core.c-196-\nkernel/liveupdate/luo_core.c:197:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-198-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c=206=late_initcall(luo_late_startup);\n--\nkernel/liveupdate/luo_core.c-210-/**\nkernel/liveupdate/luo_core.c:211: * liveupdate_reboot() - Kernel reboot notifier for live update final\nkernel/liveupdate/luo_core.c-212- * serialization.\n--\nkernel/liveupdate/luo_core.c-219- */\nkernel/liveupdate/luo_core.c:220:int liveupdate_reboot(void)\nkernel/liveupdate/luo_core.c-221-{\n--\nkernel/liveupdate/luo_core.c-223-\nkernel/liveupdate/luo_core.c:224:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-225-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c-236-/**\nkernel/liveupdate/luo_core.c:237: * liveupdate_enabled - Check if the live update feature is enabled.\nkernel/liveupdate/luo_core.c-238- *\nkernel/liveupdate/luo_core.c-239- * This function returns the state of the live update feature flag, which\nkernel/liveupdate/luo_core.c:240: * can be controlled via the ``liveupdate`` kernel command-line parameter.\nkernel/liveupdate/luo_core.c-241- *\n--\nkernel/liveupdate/luo_core.c-243- */\nkernel/liveupdate/luo_core.c:244:bool liveupdate_enabled(void)\nkernel/liveupdate/luo_core.c-245-{\n--\nkernel/liveupdate/luo_core.c-252- * The IOCTL user-space control interface for the LUO subsystem.\nkernel/liveupdate/luo_core.c:253: * It registers a character device, typically found at ``/dev/liveupdate``,\nkernel/liveupdate/luo_core.c-254- * which allows a userspace agent to manage the LUO state machine and its\n--\nkernel/liveupdate/luo_core.c-258- * to this device is exclusive: only one process is permitted to have\nkernel/liveupdate/luo_core.c:259: * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will\nkernel/liveupdate/luo_core.c-260- * fail with -EBUSY until the first process closes its file descriptor.\n--\nkernel/liveupdate/luo_core.c=270=static int luo_ioctl_create_session(struct luo_ucmd *ucmd)\nkernel/liveupdate/luo_core.c-271-{\nkernel/liveupdate/luo_core.c:272:\tstruct liveupdate_ioctl_create_session *argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-273-\tstruct file *file;\n--\nkernel/liveupdate/luo_core.c=300=static int luo_ioctl_retrieve_session(struct luo_ucmd *ucmd)\nkernel/liveupdate/luo_core.c-301-{\nkernel/liveupdate/luo_core.c:302:\tstruct liveupdate_ioctl_retrieve_session *argp = ucmd-\u003ecmd;\nkernel/liveupdate/luo_core.c-303-\tstruct file *file;\n--\nkernel/liveupdate/luo_core.c=358=union ucmd_buffer {\nkernel/liveupdate/luo_core.c:359:\tstruct liveupdate_ioctl_create_session create;\nkernel/liveupdate/luo_core.c:360:\tstruct liveupdate_ioctl_retrieve_session retrieve;\nkernel/liveupdate/luo_core.c-361-};\n--\nkernel/liveupdate/luo_core.c=380=static const struct luo_ioctl_op luo_ioctl_ops[] = {\nkernel/liveupdate/luo_core.c-381-\tIOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,\nkernel/liveupdate/luo_core.c:382:\t\t struct liveupdate_ioctl_create_session, name),\nkernel/liveupdate/luo_core.c-383-\tIOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,\nkernel/liveupdate/luo_core.c:384:\t\t struct liveupdate_ioctl_retrieve_session, name),\nkernel/liveupdate/luo_core.c-385-};\n--\nkernel/liveupdate/luo_core.c=426=static struct luo_device_state luo_dev = {\n--\nkernel/liveupdate/luo_core.c-428-\t\t.minor = MISC_DYNAMIC_MINOR,\nkernel/liveupdate/luo_core.c:429:\t\t.name = \"liveupdate\",\nkernel/liveupdate/luo_core.c-430-\t\t.fops = \u0026luo_fops,\n--\nkernel/liveupdate/luo_core.c-434-\nkernel/liveupdate/luo_core.c:435:static int __init liveupdate_ioctl_init(void)\nkernel/liveupdate/luo_core.c-436-{\nkernel/liveupdate/luo_core.c:437:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_core.c-438-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c-441-}\nkernel/liveupdate/luo_core.c:442:late_initcall(liveupdate_ioctl_init);\n"
} |
| 27/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 39930 output: 38 thoughts: 75 Thoughts: Okay, let's dive into this `liveupdate_enabled()` function. I need to understand its logic. It looks like `early_liveupdate_param` handles the parsing of the `liveupdate` flag, specifically looking for `liveupdate=on` or `liveupdate=off`. Hmm, a key question arises: is live update enabled by default, or does it *require* the `liveupdate=on` parameter? I can't rely on assumptions here. To be absolutely sure, I'm going to jump into `luo_core.c` and take a look at the code block spanning lines 75-95. That should clarify the default state and the precise conditions under which live updates are activated. Time to get to the core of the implementation. |
| 28/2 | 2026/10/28 01:47 | tool | read-file |
0mArgs:{
"File": "kernel/liveupdate/luo_core.c",
"FirstLine": 65,
"LineCount": 40
}Results: {
"Contents": " 65:\t#include \"luo_internal.h\"\n 66:\t\n 67:\tstatic struct {\n 68:\t\tbool enabled;\n 69:\t\tstruct luo_ser *luo_ser_out;\n 70:\t\tu64 liveupdate_num;\n 71:\t} luo_global;\n 72:\t\n 73:\t/*\n 74:\t * luo_register_rwlock - Protects registration of file handlers and FLBs.\n 75:\t */\n 76:\tDECLARE_RWSEM(luo_register_rwlock);\n 77:\t\n 78:\tstatic int __init early_liveupdate_param(char *buf)\n 79:\t{\n 80:\t\treturn kstrtobool(buf, \u0026luo_global.enabled);\n 81:\t}\n 82:\tearly_param(\"liveupdate\", early_liveupdate_param);\n 83:\t\n 84:\tstatic int __init luo_early_startup(void)\n 85:\t{\n 86:\t\tphys_addr_t luo_ser_phys;\n 87:\t\tstruct luo_ser *luo_ser;\n 88:\t\tsize_t len;\n 89:\t\tint err;\n 90:\t\n 91:\t\tif (!kho_is_enabled()) {\n 92:\t\t\tif (liveupdate_enabled())\n 93:\t\t\t\tpr_warn(\"Disabling liveupdate because KHO is disabled\\n\");\n 94:\t\t\tluo_global.enabled = false;\n 95:\t\t\treturn 0;\n 96:\t\t}\n 97:\t\n 98:\t\t/* Retrieve LUO state from KHO. */\n 99:\t\terr = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, \u0026luo_ser_phys, \u0026len);\n 100:\t\tif (err) {\n 101:\t\t\tif (err != -ENOENT) {\n 102:\t\t\t\tpr_err(\"failed to retrieve LUO state '%s' from KHO: %pe\\n\",\n 103:\t\t\t\t LUO_KHO_ENTRY_NAME, ERR_PTR(err));\n 104:\t\t\t\treturn err;\n"
} |
| 29/2 | 2026/10/28 01:47 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 40775 output: 19 thoughts: 16 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: **Analyzing the `kho_is_enabled()` Function** Okay, first things first, I need to get a clear picture of how this `kho_is_enabled()` function is implemented. I'm not just going to take its output at face value; I need to understand the underlying logic. What factors does it consider? Are we talking about a simple boolean check, or is there some more complex internal state or configuration involved? I'm immediately thinking about potential edge cases and dependencies. Does it rely on external resources, configuration files, environment variables, or a database lookup? What happens if any of those dependencies are unavailable or misconfigured? I'm also curious about the potential performance implications. If it's a critical path, a slow implementation here could be a bottleneck. So, a deeper dive is necessary to assess the function's reliability, efficiency, and overall impact on the system's behavior. Time to dissect the code and look for those vulnerabilities. |
| 30/2 | 2026/10/28 01:48 | tool | grepper |
0mArgs:{
"Expression": "kho_is_enabled"
}Results: {
"Output": "include/linux/kexec_handover.h=14=struct page;\n--\ninclude/linux/kexec_handover.h-16-#ifdef CONFIG_KEXEC_HANDOVER\ninclude/linux/kexec_handover.h:17:bool kho_is_enabled(void);\ninclude/linux/kexec_handover.h-18-bool is_kho_boot(void);\n--\ninclude/linux/kexec_handover.h=44=static inline enum migratetype kho_scratch_migratetype(unsigned long pfn,\n--\ninclude/linux/kexec_handover.h-51-#else\ninclude/linux/kexec_handover.h:52:static inline bool kho_is_enabled(void)\ninclude/linux/kexec_handover.h-53-{\n--\nkernel/kexec_file.c=813=static int kexec_calculate_store_digests(struct kimage *image)\n--\nkernel/kexec_file.c-845-\tif (image-\u003etype != KEXEC_TYPE_CRASH \u0026\u0026\nkernel/kexec_file.c:846:\t (kho_is_enabled() || kexec_only_cma_segments(image))) {\nkernel/kexec_file.c-847-\t\tpr_debug(\"disabling checksum verification in purgatory\\n\");\n--\nkernel/liveupdate/kexec_handover.c=69=static bool kho_enable __ro_after_init = IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);\nkernel/liveupdate/kexec_handover.c-70-\nkernel/liveupdate/kexec_handover.c:71:bool kho_is_enabled(void)\nkernel/liveupdate/kexec_handover.c-72-{\n--\nkernel/liveupdate/kexec_handover.c-74-}\nkernel/liveupdate/kexec_handover.c:75:EXPORT_SYMBOL_GPL(kho_is_enabled);\nkernel/liveupdate/kexec_handover.c-76-\n--\nkernel/liveupdate/luo_core.c=84=static int __init luo_early_startup(void)\n--\nkernel/liveupdate/luo_core.c-90-\nkernel/liveupdate/luo_core.c:91:\tif (!kho_is_enabled()) {\nkernel/liveupdate/luo_core.c-92-\t\tif (liveupdate_enabled())\n--\nlib/test_kho.c=314=static int __init kho_test_init(void)\n--\nlib/test_kho.c-318-\nlib/test_kho.c:319:\tif (!kho_is_enabled())\nlib/test_kho.c-320-\t\treturn 0;\n--\nmm/memblock.c=2701=static int __init reserve_mem_init(void)\n--\nmm/memblock.c-2704-\nmm/memblock.c:2705:\tif (!kho_is_enabled() || !reserved_mem_count)\nmm/memblock.c-2706-\t\treturn 0;\n"
} |
| 31/2 | 2026/10/28 01:48 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 41808 output: 18 thoughts: 69 Thoughts: Here's my take on those thoughts: **Considering Live Update Configuration** Okay, so I'm thinking about how the live update functionality is configured. I'm wondering if there's a default setting, maybe something like `LIVEUPDATE_DEFAULT`? It’s probably a macro, but I need to see what it's set to. Let's look at `early_liveupdate_param` to get a better idea. Right, the `enabled` flag is defined as a `static bool`. The documentation says that it's initially `false` unless `liveupdate=on` is specified in the boot parameters, or if `CONFIG_LIVEUPDATE_ENABLE_DEFAULT` is defined. Therefore, I need to know what the default enable configuration is set to. I should check if there’s a default enable setting for liveupdate so I understand how it behaves out of the box. |
| 32/2 | 2026/10/28 01:49 | tool | grepper |
0mError:no matches Args: {
"Expression": "LIVEUPDATE.*DEFAULT"
}Results: {
"error": "no matches"
} |
| 33/2 | 2026/10/28 01:49 | llm | patch-evaluator |
2mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 42098 output: 39 thoughts: 1922 Thoughts: **Fuzzing Analysis: This Patch is Definitely Worthy** Okay, so I'm looking at this patch and my initial thought is: syzkaller should *definitely* be given a shot at it, either using kernel command-line options or through QEMU. But wait, is this just for live patching, or are we dealing with core memory management changes? I need to stay sharp here. Let's see what the fuzzing guidelines tell me. Alright, the guidelines are clear: reachability is king. Since the patch touches core subsystems, I know I need to dig deeper. They emphasize not taking "no functional change" claims at face value, and refactorings *always* get a second look. Any modification to reachable code is worth the effort to fuzz. And the changes... Whoa. This hits a bunch of core memory management and VFS files: `fs/inode.c`, `mm/filemap.c`, `mm/huge_memory.c`, `mm/khugepaged.c`, `mm/migrate.c`, `mm/shmem.c`, `mm/truncate.c`, and `mm/vmscan.c`. Massive. It's not just logic changes, it's also adding *new* runtime assertions! I see WARN_ON_ONCE and VM_WARN_ON_ONCE checks popping up all over the place, like `mapping_frozen(&inode->i_data)` and `mapping_frozen(mapping)`. This is a classic: even if the author *thinks* the invariant holds, fuzzing is essential to verify it. That's a good start. The patch isn't just adding assertions, it *modifies* core logic: there are numerous checks of `mapping_frozen(mapping)` within various functions like `__filemap_add_folio`, `folio_check_splittable`, `__folio_freeze_split_file`, `collapse_file`, `__folio_migrate_mapping`, etc. This means even if the patch *doesn't* introduce a new bug, it still is adding another layer of logic to already complicated processes. I'm starting to see that this involves a significant refactoring of how memfd live-update operations. I see `memfd_luo_preserve_folios()` being rewritten, replacing `memfd_pin_folios()` with a custom loop with `shmem_get_folio()`, `memfd_luo_migrate_folio()`, and `migrate_pages`! This is getting interesting. Now, I see `mapping_set_frozen(inode->i_mapping)` being set! This means, while the mapping is frozen, userspace *can* still do things like read, write, truncate, map, unmap, evict, migrate, split, collapse, swap, and evict the inode. Okay, here's where it gets really interesting and where the fuzzing campaign needs to be targeted. The critical question becomes what happens if userspace closes the memfd while it's frozen? Is there a race condition? I see a WARN_ON_ONCE in `fs/inode.c` specifically addressing this. The code says that if `mapping_frozen(&inode->i_data)` is true, something has gone wrong, so we clear the `AS_FROZEN` flag. I have a suspicion here. I need to dive into `memfd_luo.c` and `luo_file.c` to understand exactly how the references are handled. It seems like a race condition between `memfd_luo_preserve()` and userspace operations or closing the file descriptor is possible. I need to see *how* these references are held, and how the file descriptors are handled. This has fuzzing campaign written all over it. |
| 34/2 | 2026/10/28 01:51 | tool | read-file |
0mArgs:{
"File": "kernel/liveupdate/luo_file.c",
"FirstLine": 230,
"LineCount": 50
}Results: {
"Contents": " 230:\tint luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)\n 231:\t{\n 232:\t\tstruct liveupdate_file_op_args args = {0};\n 233:\t\tstruct liveupdate_file_handler *fh;\n 234:\t\tstruct luo_file *luo_file;\n 235:\t\tstruct file *file;\n 236:\t\tint err;\n 237:\t\n 238:\t\tif (luo_token_is_used(file_set, token))\n 239:\t\t\treturn -EEXIST;\n 240:\t\n 241:\t\terr = kho_block_set_grow(\u0026file_set-\u003eblock_set, file_set-\u003ecount + 1);\n 242:\t\tif (err)\n 243:\t\t\treturn err;\n 244:\t\n 245:\t\tfile = fget(fd);\n 246:\t\tif (!file) {\n 247:\t\t\terr = -EBADF;\n 248:\t\t\tgoto err_shrink;\n 249:\t\t}\n 250:\t\n 251:\t\terr = -ENOENT;\n 252:\t\tdown_read(\u0026luo_register_rwlock);\n 253:\t\tlist_private_for_each_entry(fh, \u0026luo_file_handler_list, list) {\n 254:\t\t\tif (fh-\u003eops-\u003ecan_preserve(fh, file)) {\n 255:\t\t\t\tif (try_module_get(fh-\u003eops-\u003eowner))\n 256:\t\t\t\t\terr = 0;\n 257:\t\t\t\tbreak;\n 258:\t\t\t}\n 259:\t\t}\n 260:\t\tup_read(\u0026luo_register_rwlock);\n 261:\t\n 262:\t\t/* err is still -ENOENT if no handler was found */\n 263:\t\tif (err)\n 264:\t\t\tgoto err_fput;\n 265:\t\n 266:\t\terr = xa_insert(\u0026luo_preserved_files, luo_get_id(fh, file),\n 267:\t\t\t\tfile, GFP_KERNEL);\n 268:\t\tif (err)\n 269:\t\t\tgoto err_module_put;\n 270:\t\n 271:\t\terr = luo_flb_file_preserve(fh);\n 272:\t\tif (err)\n 273:\t\t\tgoto err_erase_xa;\n 274:\t\n 275:\t\tluo_file = kzalloc_obj(*luo_file);\n 276:\t\tif (!luo_file) {\n 277:\t\t\terr = -ENOMEM;\n 278:\t\t\tgoto err_flb_unpreserve;\n 279:\t\t}\n"
} |
| 35/2 | 2026/10/28 01:51 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 45609 output: 39 thoughts: 27 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving Deeper into the Preserve Operation** Right, let's get down to brass tacks. I need to understand the control flow surrounding `fh->ops->preserve()` within `luo_file.c`. My immediate goal is to trace the execution path that leads to this specific function call. Knowing the surrounding code, the context in which `preserve()` is invoked, and what data structures are in play is crucial for a comprehensive understanding of the file handling mechanism. I'm looking for the calling conventions, the arguments passed to this function, and any potential error handling that surrounds its invocation. This detail is going to be key to debugging, optimizing or modifying the file system code later. |
| 36/2 | 2026/10/28 01:52 | tool | read-file |
0mArgs:{
"File": "kernel/liveupdate/luo_file.c",
"FirstLine": 280,
"LineCount": 40
}Results: {
"Contents": " 280:\t\n 281:\t\tluo_file-\u003efile = file;\n 282:\t\tluo_file-\u003efh = fh;\n 283:\t\tluo_file-\u003etoken = token;\n 284:\t\tmutex_init(\u0026luo_file-\u003emutex);\n 285:\t\n 286:\t\targs.handler = fh;\n 287:\t\targs.file = file;\n 288:\t\terr = fh-\u003eops-\u003epreserve(\u0026args);\n 289:\t\tif (err)\n 290:\t\t\tgoto err_kfree;\n 291:\t\n 292:\t\tluo_file-\u003eserialized_data = args.serialized_data;\n 293:\t\tluo_file-\u003eprivate_data = args.private_data;\n 294:\t\tlist_add_tail(\u0026luo_file-\u003elist, \u0026file_set-\u003efiles_list);\n 295:\t\tfile_set-\u003ecount++;\n 296:\t\n 297:\t\treturn 0;\n 298:\t\n 299:\terr_kfree:\n 300:\t\tkfree(luo_file);\n 301:\terr_flb_unpreserve:\n 302:\t\tluo_flb_file_unpreserve(fh);\n 303:\terr_erase_xa:\n 304:\t\txa_erase(\u0026luo_preserved_files, luo_get_id(fh, file));\n 305:\terr_module_put:\n 306:\t\tmodule_put(fh-\u003eops-\u003eowner);\n 307:\terr_fput:\n 308:\t\tfput(file);\n 309:\terr_shrink:\n 310:\t\tkho_block_set_shrink(\u0026file_set-\u003eblock_set, file_set-\u003ecount);\n 311:\t\n 312:\t\treturn err;\n 313:\t}\n 314:\t\n 315:\t/**\n 316:\t * luo_file_unpreserve_files - Unpreserves all files from a file_set.\n 317:\t * @file_set: The files to be cleaned up.\n 318:\t *\n 319:\t * This function serves as the primary cleanup path for a file_set. It is\n"
} |
| 37/2 | 2026/10/28 01:52 | llm | patch-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 46434 output: 37 thoughts: 1174 Thoughts: **Analyzing the Live Update Memfd Implementation** Okay, so `luo_file` effectively keeps a file descriptor (`fd`) alive with `fget()` until it's either unpreserved or destroyed. My primary focus right now is understanding what can go wrong – or more accurately, *what* is intentionally prevented – when a memfd is in a frozen state. It's a comprehensive list: * Any operation on the memfd file descriptor is blocked: `fallocate()`, `ftruncate()`, `write()`, `mmap()`/page faulting (new folio or THP split), khugepaged collapse, page migration, swapout/swapin, page reclaim, inode eviction, truncation, shmem undo range, and page cache deletion. The kernel is *asserting* the frozen state via warnings if someone tries to call any of these. This touches a significant portion of core memory management: It introduces a new `AS_FROZEN` state and has implications across page migration, shmem, truncation, filemap, huge memory, khugepaged, and vmscan subsystems. `memfd_luo.c` itself now has been rewritten, and there are many `WARN_ON_ONCE` and `VM_WARN_ON_ONCE` checks to ensure that nobody inadvertently messes up the state. This definitively falls under section 3, encompassing core subsystems, refactorings/cleanups, and, crucially, runtime assertions and defensive checks. *This is definitely WorthFuzzing.* Now, let's look at the kernel configs required to enable this. 1. `AS_FROZEN` and corresponding code changes in `fs/inode.c`, `mm/filemap.c`, `mm/truncate.c`, and `mm/vmscan.c` are built unconditionally. 2. `mm/huge_memory.c` and `mm/khugepaged.c` need `CONFIG_TRANSPARENT_HUGEPAGE`. 3. `mm/migrate.c` requires `CONFIG_MIGRATION`. 4. `mm/shmem.c` requires `CONFIG_SHMEM`. 5. What about `mm/memfd_luo.c`? `mm/Makefile` shows that it depends on `CONFIG_LIVEUPDATE_MEMFD`. Tracing `CONFIG_LIVEUPDATE_MEMFD`, it depends on `LIVEUPDATE`, which in turn depends on `KEXEC_HANDOVER`, that then has further dependencies on architecture specific features like `ARCH_SUPPORTS_KEXEC_HANDOVER`, `ARCH_SUPPORTS_KEXEC_FILE`, `MEMBLOCK_KHO_SCRATCH`, `KEXEC_FILE`, `LIBFDT`, and `CMA`. We also need `CONFIG_MEMFD_CREATE`. Ok, I need to check `grep` what depends on `CONFIG_MEMFD_CREATE` to ensure it is supported on the target architecture. |
| 38/2 | 2026/10/28 01:53 | tool | grepper |
0mArgs:{
"Expression": "config MEMFD_CREATE\\b",
"PathPrefixes": [
"init/Kconfig",
"mm/"
]
}Results: {
"Output": "mm/Kconfig=1333=config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY\n--\nmm/Kconfig-1335-\nmm/Kconfig:1336:config MEMFD_CREATE\nmm/Kconfig-1337-\tbool \"Enable memfd_create() system call\" if EXPERT\n"
} |
| 39/2 | 2026/10/28 01:53 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 48370 output: 20 thoughts: 279 Thoughts: **My Configuration Investigation** Okay, let's break down the configuration requirements for this live update process. I need to figure out which kernel configurations are essential. I see `LIVEUPDATE_MEMFD` is a dependency, which in turn relies on `LIVEUPDATE`, `MEMFD_CREATE`, and `SHMEM`. Right, and we also have `KEXEC_HANDOVER`, `TRANSPARENT_HUGEPAGE`, and `MIGRATION` to consider. Now, a crucial question pops up: does `KEXEC_HANDOVER_ENABLE_DEFAULT` actually help enable KHO without the need for a boot parameter? I need to verify that. Let's delve into `kernel/liveupdate/kexec_handover.c` to confirm. Ah, here it is: `static bool kho_enable __ro_after_init = IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);` Perfect! It does enable KHO by default. Excellent. Now, what enables the `liveupdate` functionality itself? Does it require a command-line parameter, or is there a specific kernel config that controls it? I need to investigate `kernel/liveupdate/luo_core.c` for some clues. I'll check `early_liveupdate_param` again. On line 80, I see `return kstrtobool(buf, &luo_global.enabled);`. Hmm, it appears that the global `luo_global.enabled` is controlled by this early parameter. But is `luo_global.enabled` initialized anywhere else? Or is it *only* determined by the early parameter? I need to search through the code to be sure. I'll use grep to see where `luo_global.enabled` is referenced and initialized. |
| 40/2 | 2026/10/28 01:53 | tool | grepper |
0mArgs:{
"Expression": "luo_global\\.enabled"
}Results: {
"Output": "kernel/liveupdate/luo_core.c=78=static int __init early_liveupdate_param(char *buf)\nkernel/liveupdate/luo_core.c-79-{\nkernel/liveupdate/luo_core.c:80:\treturn kstrtobool(buf, \u0026luo_global.enabled);\nkernel/liveupdate/luo_core.c-81-}\n--\nkernel/liveupdate/luo_core.c=84=static int __init luo_early_startup(void)\n--\nkernel/liveupdate/luo_core.c-93-\t\t\tpr_warn(\"Disabling liveupdate because KHO is disabled\\n\");\nkernel/liveupdate/luo_core.c:94:\t\tluo_global.enabled = false;\nkernel/liveupdate/luo_core.c-95-\t\treturn 0;\n--\nkernel/liveupdate/luo_core.c=138=static int __init liveupdate_early_init(void)\n--\nkernel/liveupdate/luo_core.c-143-\tif (err) {\nkernel/liveupdate/luo_core.c:144:\t\tluo_global.enabled = false;\nkernel/liveupdate/luo_core.c-145-\t\tluo_restore_fail(\"The incoming tree failed to initialize properly [%pe], disabling live update\\n\",\n--\nkernel/liveupdate/luo_core.c=193=static int __init luo_late_startup(void)\n--\nkernel/liveupdate/luo_core.c-201-\tif (err)\nkernel/liveupdate/luo_core.c:202:\t\tluo_global.enabled = false;\nkernel/liveupdate/luo_core.c-203-\n--\nkernel/liveupdate/luo_core.c=244=bool liveupdate_enabled(void)\nkernel/liveupdate/luo_core.c-245-{\nkernel/liveupdate/luo_core.c:246:\treturn luo_global.enabled;\nkernel/liveupdate/luo_core.c-247-}\n"
} |
| 41/2 | 2026/10/28 01:54 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 49588 output: 31 thoughts: 477 Thoughts: **Analyzing Liveupdate and Related Kernel Configurations** Okay, so I'm looking at this patch and trying to understand the configuration implications for live updates in the kernel. The core of it seems to be tied to the `liveupdate` command-line parameter, which either gets invoked at boot or through syzkaller. From a Kconfig standpoint, the important ones jump out: `LIVEUPDATE`, `LIVEUPDATE_MEMFD`, `KEXEC_HANDOVER`, `KEXEC_HANDOVER_ENABLE_DEFAULT`, `MEMFD_CREATE`, `SHMEM`, `TRANSPARENT_HUGEPAGE`, and `MIGRATION`. Now, I need to dig deeper. Let's see if this patch introduces any new config dependencies that aren't immediately obvious. I'm going to inspect the diff file-by-file. * `fs/inode.c`: Alright, nothing related to those configs here. Looks like the `evict()` function isn't conditionally compiled based on any of these. * `include/linux/pagemap.h`: Just inline functions, so nothing to flag for configuration. * `include/linux/shmem_fs.h`: Header files, again not dependent on any config. * `mm/filemap.c`: Okay, there are some functions in here, specifically `page_cache_delete`, `page_cache_delete_batch`, `replace_page_cache_folio`, and `__filemap_add_folio`. I'll keep an eye on them for now. * `mm/huge_memory.c`: This one's interesting. `folio_check_splittable` and `__folio_freeze_split_file` are in there, both guarded by `CONFIG_TRANSPARENT_HUGEPAGE`. That's a key dependency. * `mm/khugepaged.c`: `collapse_file` is also guarded by `CONFIG_TRANSPARENT_HUGEPAGE`, reinforcing the importance of that configuration option. * `mm/memfd_luo.c`: And here we have `CONFIG_LIVEUPDATE_MEMFD=y` which means that the functions in here are compiled only when `LIVEUPDATE_MEMFD` is enabled. * `mm/migrate.c`: This one's important: `__folio_migrate_mapping` and `migrate_huge_page_move_mapping` are dependent on `CONFIG_MIGRATION`. * `mm/shmem.c`: Quite a few functions are impacted here: `shmem_add_to_page_cache`, `shmem_undo_range`, `shmem_setattr`, `shmem_writeout`, `shmem_swapin_folio`, and `shmem_fallocate`. They're all dependent on `CONFIG_SHMEM`. * `mm/truncate.c`: functions related to `folio` handling like `truncate_inode_folio`, `mapping_evict_folio`, `truncate_inode_pages_range`, `folio_unmap_invalidate`. * `mm/vmscan.c`: I see a call to `__remove_mapping`. Next, I need to check the dependencies of `CONFIG_MIGRATION` in the Kconfig. I want to see how these different configurations interrelate. |
| 42/2 | 2026/10/28 01:54 | tool | grepper |
0mArgs:{
"Expression": "config MIGRATION\\b",
"PathPrefixes": [
"mm/Kconfig"
]
}Results: {
"Output": "mm/Kconfig=672=config NUMA_MIGRATION\n--\nmm/Kconfig-682-\nmm/Kconfig:683:config MIGRATION\nmm/Kconfig-684-\tbool\n"
} |
| 43/2 | 2026/10/28 01:54 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 50883 output: 20 thoughts: 13 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: **Investigating the `CONFIG_MIGRATION` Selection** Alright, let's dive in. I need to understand the implications of `CONFIG_MIGRATION` and how it's being selected. My intuition tells me this is likely related to data migration strategies or potentially feature toggling related to a migration process. I want to see precisely *what* is selecting it. I need to trace the dependencies. Is it a direct configuration option somewhere, or is it being pulled in based on other selections? Are there any conditional dependencies I should be aware of? I need to know the decision path. Understanding the context surrounding this config is paramount for me, since the consequences of making a change could be significant. Is it core, or a more peripheral feature? Are there any potential conflicts I need to be aware of? I should also check to see if there are any associated documentation or build-time tools for dealing with data migration. I need to ensure this is sound, efficient, and well-integrated. Let's start with a thorough investigation of the relevant Kconfig files. Time to dig in! |
| 44/2 | 2026/10/28 01:54 | tool | grepper |
0mArgs:{
"Expression": "select MIGRATION\\b"
}Results: {
"Output": "mm/Kconfig=581=config MEMORY_HOTREMOVE\nmm/Kconfig-582-\tbool \"Allow for memory hot remove\"\nmm/Kconfig:583:\tselect MIGRATION\nmm/Kconfig-584-\n--\nmm/Kconfig=641=config COMPACTION\n--\nmm/Kconfig-643-\tdefault y\nmm/Kconfig:644:\tselect MIGRATION\nmm/Kconfig-645-\tdepends on MMU\n--\nmm/Kconfig=672=config NUMA_MIGRATION\n--\nmm/Kconfig-675-\tdepends on NUMA \u0026\u0026 MMU\nmm/Kconfig:676:\tselect MIGRATION\nmm/Kconfig-677-\thelp\n--\nmm/Kconfig=764=config MEMORY_FAILURE\n--\nmm/Kconfig-768-\tselect INTERVAL_TREE\nmm/Kconfig:769:\tselect MIGRATION\nmm/Kconfig-770-\thelp\n--\nmm/Kconfig=1055=config CMA\n--\nmm/Kconfig-1057-\tdepends on MMU\nmm/Kconfig:1058:\tselect MIGRATION\nmm/Kconfig-1059-\tselect MEMORY_ISOLATION\n"
} |
| 45/2 | 2026/10/28 01:54 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 51494 output: 21 thoughts: 537 Thoughts: **My Analysis of FocusSymbols for Fuzzing** Okay, so `COMPACTION` automatically enables `MIGRATION`, and `CMA` also relies on `MIGRATION` due to `KEXEC_HANDOVER`. Got it. Now, let's dive into FocusSymbols. I need to be precise here, as I know that dilution is the enemy of effective fuzzing. The instructions are clear: when `WorthFuzzing` is true, I must extract specific kernel functions into `FocusSymbols` to really guide the fuzzer. It’s all about preventing dilution. I've got to avoid generic functions that are called everywhere, the usual suspects like memory allocators, deallocators, page fault handlers, and core synchronization primitives. Listing those just makes the fuzzer chase its tail and classify everything as "focused," wasting its efforts. Instead, I need to pinpoint the *specific* feature logic or API entrypoints related to the changes. I need to be especially mindful of static inline functions in headers. They don't have distinct symbols in `vmlinux`, so I can't target them directly. If the changes are mainly in those static inline helpers, I'll have to find non-static, feature-specific callers in the `.c` files that exercise them, avoiding the ubiquitous wrappers. Now, let's look at the functions modified or added by this patch, starting with `fs/inode.c`: I see `evict`. Hmm, that's called when an inode's reference count drops to zero, which happens when files are closed. That's *very* common. I'm going to be cautious with `evict`; it likely qualifies as a ubiquitous lifecycle hot-path. Next, I see `include/linux/pagemap.h`. It contains `mapping_set_frozen`, `mapping_clear_frozen`, and `mapping_frozen`. Static inlines, all in the header, so I can't target them directly. Finally, in `mm/filemap.c`, I see `page_cache_delete` and `page_cache_delete_batch`, which are static helpers. But I also see `replace_page_cache_folio`. It’s non-static, so it could be viable, but is it ubiquitous? I need to check the callers of `replace_page_cache_folio` to be sure. I can’t waste time on a function that is ubiquitous. |
| 46/2 | 2026/10/28 01:54 | tool | grepper |
0mArgs:{
"Expression": "replace_page_cache_folio"
}Results: {
"Output": "fs/fuse/dev.c=1123=static int fuse_try_move_folio(struct fuse_copy_state *cs, struct folio **foliop)\n--\nfs/fuse/dev.c-1181-\nfs/fuse/dev.c:1182:\treplace_page_cache_folio(oldfolio, newfolio);\nfs/fuse/dev.c-1183-\n--\ninclude/linux/pagemap.h=1382=void __filemap_remove_folio(struct folio *folio, void *shadow);\ninclude/linux/pagemap.h:1383:void replace_page_cache_folio(struct folio *old, struct folio *new);\ninclude/linux/pagemap.h-1384-void delete_from_page_cache_batch(struct address_space *mapping,\n--\nmm/filemap.c=798=EXPORT_SYMBOL(file_write_and_wait_range);\n--\nmm/filemap.c-800-/**\nmm/filemap.c:801: * replace_page_cache_folio - replace a pagecache folio with a new one\nmm/filemap.c-802- * @old:\tfolio to be replaced\n--\nmm/filemap.c-812- */\nmm/filemap.c:813:void replace_page_cache_folio(struct folio *old, struct folio *new)\nmm/filemap.c-814-{\n--\nmm/filemap.c-848-}\nmm/filemap.c:849:EXPORT_SYMBOL_GPL(replace_page_cache_folio);\nmm/filemap.c-850-\n"
} |
| 47/2 | 2026/10/28 01:54 | llm | patch-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 52993 output: 21 thoughts: 153 Thoughts: Okay, let me break this down. **Diving into Folio Replacement and Split Operations** Right, so `replace_page_cache_folio`... that's only called in `fuse_try_move_folio`? Hmm, quite a niche use-case, but I need to remember that. And then, hold on, wasn't there a recent modification to that function? Something I should check into. But I'm more interested in the broader picture. Now, where are *folios* actually *added* to the page cache? Ah, right, `__filemap_add_folio`. Now *that's* a function called all over the place – reads, writes, everything! That's the key entry point. That's a much more significant and universal area to watch. Next, I need to get my hands on the huge memory code (`mm/huge_memory.c`). Let's see... I see `folio_check_splittable` and, interestingly, `__folio_freeze_split_file` is there. It's marked as static, which would limit its use, but it's called by `split_huge_page_to_list_to_order`. That's important. I need to make sure that `folio_check_splittable` is available globally. I should check if it's a global symbol or internal to the huge memory code. |
| 48/2 | 2026/10/28 01:56 | tool | grepper |
0mArgs:{
"Expression": "folio_check_splittable"
}Results: {
"Output": "include/linux/huge_mm.h=407=int split_folio_to_list(struct folio *folio, struct list_head *list);\ninclude/linux/huge_mm.h:408:int folio_check_splittable(struct folio *folio, unsigned int new_order,\ninclude/linux/huge_mm.h-409-\t\t\t enum split_type split_type);\n--\nmm/huge_memory.c=3851=static int __split_frozen_folio(struct folio *folio, int new_order,\n--\nmm/huge_memory.c-3918-/**\nmm/huge_memory.c:3919: * folio_check_splittable() - check if a folio can be split to a given order\nmm/huge_memory.c-3920- * @folio: folio to be split\n--\nmm/huge_memory.c-3925- *\nmm/huge_memory.c:3926: * folio_check_splittable() checks if @folio can be split to @new_order using\nmm/huge_memory.c-3927- * @split_type method. The truncated folio check must come first.\n--\nmm/huge_memory.c-3933- */\nmm/huge_memory.c:3934:int folio_check_splittable(struct folio *folio, unsigned int new_order,\nmm/huge_memory.c-3935-\t\t\t enum split_type split_type)\n--\nmm/huge_memory.c=4310=static int __folio_split(struct folio *folio, unsigned int new_order,\n--\nmm/huge_memory.c-4333-\nmm/huge_memory.c:4334:\tret = folio_check_splittable(folio, new_order, split_type);\nmm/huge_memory.c-4335-\tif (ret) {\n"
} |
| 49/2 | 2026/10/28 01:56 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 53950 output: 32 thoughts: 67 Thoughts: Here's my summary, as I see it: **Investigating a Potential Issue in Kernel Memory Management** Okay, so I'm looking at `folio_check_splittable`. It's exported, so it's accessible from outside its originating compilation unit, which means its usage is broader than initially expected. That's good to know, right off the bat. Now, I'm diving into `mm/khugepaged.c`. My initial thought is to examine the `collapse_file` function. It *appears* to be static, which would limit its visibility. However, I need to confirm this assumption. I suspect it might be called from somewhere related to khugepaged, perhaps through `khugepaged_collapse_file` or a similarly named function. The goal here is to determine whether there's some sort of linkage or relationship between these different components. I need to trace the call paths to be absolutely certain. Let's dig in. |
| 50/2 | 2026/10/28 01:56 | tool | grepper |
0mArgs:{
"Expression": "collapse_file",
"PathPrefixes": [
"mm/khugepaged.c"
]
}Results: {
"Output": "mm/khugepaged.c=2120=static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)\n--\nmm/khugepaged.c-2204-/**\nmm/khugepaged.c:2205: * collapse_file - collapse filemap/tmpfs/shmem pages into huge one.\nmm/khugepaged.c-2206- *\n--\nmm/khugepaged.c-2228- */\nmm/khugepaged.c:2229:static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,\nmm/khugepaged.c-2230-\t\tstruct file *file, pgoff_t start, struct collapse_control *cc)\n--\nmm/khugepaged.c-2674-\tVM_BUG_ON(!list_empty(\u0026pagelist));\nmm/khugepaged.c:2675:\ttrace_mm_khugepaged_collapse_file(mm, new_pfn, index, addr, is_shmem, file, HPAGE_PMD_NR, result);\nmm/khugepaged.c-2676-\treturn result;\n--\nmm/khugepaged.c=2827=static enum scan_result collapse_pmd(struct mm_struct *mm,\n--\nmm/khugepaged.c-2844-retry:\nmm/khugepaged.c:2845:\tresult = collapse_file(mm, addr, file, pgoff, cc);\nmm/khugepaged.c-2846-\n"
} |
| 51/2 | 2026/10/28 01:56 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 54673 output: 23 thoughts: 506 Thoughts: **Analyzing the Live Update Mechanism for Memfd Objects** Alright, let's dive into this. My initial focus is on `mm/memfd_luo.c`. I need to understand how the live update operations are being handled for memfd objects. The key functions here appear to be `memfd_luo_preserve_folios`, `memfd_luo_preserve_folio`, `memfd_luo_migrate_folio`, `memfd_luo_put_folios`, `memfd_luo_unpreserve_folios`, `memfd_luo_preserve`, and `memfd_luo_unpreserve`. Aha! `memfd_luo_preserve` is the handler callback, part of the `liveupdate_file_ops` struct. That's the core. It looks like it's setting `mapping_set_frozen`, `mapping_clear_frozen`, migrating folios, and preserving them all in one fell swoop! This is accessed through the `LIVEUPDATE_SESSION_PRESERVE_FD` ioctl via `luo_preserve_file()`. Ok, so that's the user-space entry point. I should also check `kernel/liveupdate/luo_session.c` for how the user initiates this, and I see `luo_session_preserve_fd`. Looks like that's the main entry point for the user-space function. Now, to understand the migration process, I need to look at `mm/migrate.c`. I see `__folio_migrate_mapping` and `migrate_huge_page_move_mapping`. I'll confirm that `migrate_huge_page_move_mapping` is non-static to ensure it's accessible where I think it is. I'm especially interested in how `mm/memfd_luo.c`'s functions integrate with the folio migration routines in `mm/migrate.c`. |
| 52/2 | 2026/10/28 01:57 | tool | grepper |
0mArgs:{
"Expression": "migrate_huge_page_move_mapping"
}Results: {
"Output": "fs/hugetlbfs/inode.c=1024=static int hugetlbfs_migrate_folio(struct address_space *mapping,\n--\nfs/hugetlbfs/inode.c-1029-\nfs/hugetlbfs/inode.c:1030:\trc = migrate_huge_page_move_mapping(mapping, dst, src);\nfs/hugetlbfs/inode.c-1031-\tif (rc)\n--\ninclude/linux/migrate.h=65=bool isolate_folio_to_list(struct folio *folio, struct list_head *list);\ninclude/linux/migrate.h-66-\ninclude/linux/migrate.h:67:int migrate_huge_page_move_mapping(struct address_space *mapping,\ninclude/linux/migrate.h-68-\t\tstruct folio *dst, struct folio *src);\n--\ninclude/linux/migrate.h=89=static inline bool isolate_folio_to_list(struct folio *folio, struct list_head *list)\n--\ninclude/linux/migrate.h-91-\ninclude/linux/migrate.h:92:static inline int migrate_huge_page_move_mapping(struct address_space *mapping,\ninclude/linux/migrate.h-93-\t\t\t\t struct folio *dst, struct folio *src)\n--\nmm/migrate.c=739=EXPORT_SYMBOL(folio_migrate_mapping);\n--\nmm/migrate.c-744- */\nmm/migrate.c:745:int migrate_huge_page_move_mapping(struct address_space *mapping,\nmm/migrate.c-746-\t\t\t\t struct folio *dst, struct folio *src)\n"
} |
| 53/2 | 2026/10/28 01:57 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 56037 output: 31 thoughts: 25 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: **My Initial Assessment of Folio Migration** Alright, so I'm looking at this `folio_migrate_mapping` function within `mm/migrate.c`. My immediate thought is, "Okay, this is where the core logic for migrating folio mappings resides." From what I remember of the code, this is a pivotal point in the process. Then, I see it calls `__folio_migrate_mapping`. That immediately tells me a few things: this is likely the internal, lower-level workhorse behind the high-level `folio_migrate_mapping`. It probably handles the nitty-gritty details of the migration itself, potentially including things like updating page table entries, managing locks, and dealing with any specific architectural nuances. This suggests that the external-facing function, `folio_migrate_mapping`, might handle the setup and sanity checks, while this internal one does the main migration work. I need to dig deeper into the actual implementation of `__folio_migrate_mapping` to understand the granular aspects of how folio mappings are handled. |
| 54/2 | 2026/10/28 01:57 | tool | grepper |
0mArgs:{
"Expression": "folio_migrate_mapping",
"PathPrefixes": [
"mm/migrate.c"
]
}Results: {
"Output": "mm/migrate.c=561=void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)\n--\nmm/migrate.c-582- */\nmm/migrate.c:583:static int __folio_migrate_mapping(struct address_space *mapping,\nmm/migrate.c-584-\t\tstruct folio *newfolio, struct folio *folio, int expected_count)\n--\nmm/migrate.c-728-\nmm/migrate.c:729:int folio_migrate_mapping(struct address_space *mapping,\nmm/migrate.c-730-\t\tstruct folio *newfolio, struct folio *folio, int extra_count)\n--\nmm/migrate.c-736-\nmm/migrate.c:737:\treturn __folio_migrate_mapping(mapping, newfolio, folio, expected_count);\nmm/migrate.c-738-}\nmm/migrate.c:739:EXPORT_SYMBOL(folio_migrate_mapping);\nmm/migrate.c-740-\n--\nmm/migrate.c-742- * The expected number of remaining references is the same as that\nmm/migrate.c:743: * of folio_migrate_mapping().\nmm/migrate.c-744- */\n--\nmm/migrate.c=785=void folio_migrate_flags(struct folio *newfolio, struct folio *folio)\n--\nmm/migrate.c-811-\nmm/migrate.c:812:\t/* Move dirty on pages not done by folio_migrate_mapping() */\nmm/migrate.c-813-\tif (folio_test_dirty(folio))\n--\nmm/migrate.c=879=static int __migrate_folio(struct address_space *mapping, struct folio *dst,\n--\nmm/migrate.c-892-\nmm/migrate.c:893:\trc = __folio_migrate_mapping(mapping, dst, src, expected_count);\nmm/migrate.c-894-\tif (rc)\n--\nmm/migrate.c=1372=static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,\n--\nmm/migrate.c-1407-\t * the source was on the queue. The source is unqueued in\nmm/migrate.c:1408:\t * __folio_migrate_mapping(), so we recorded the state from\nmm/migrate.c-1409-\t * before move_to_new_folio().\n"
} |
| 55/2 | 2026/10/28 01:57 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 56964 output: 403 thoughts: 2337 Thoughts: **Focus Symbol Determination for Fuzzing with Live Update and Memfd** Okay, so I've been tasked with identifying key functions to focus fuzzing efforts related to the recent kernel changes. I'm seeing that `folio_migrate_mapping` calls `__folio_migrate_mapping`, and that a `mapping_frozen` check has been added there. I need to be precise about what should be targeted. First, I examined several core memory management files. In `mm/shmem.c`, I identified modifications in functions like `shmem_add_to_page_cache`, `shmem_undo_range`, `shmem_setattr`, `shmem_writeout`, `shmem_swapin_folio`, and `shmem_fallocate`. Then, I looked at `mm/truncate.c`, where `truncate_inode_folio`, `mapping_evict_folio`, `truncate_inode_pages_range`, and `folio_unmap_invalidate` have been updated. Finally, I noted the role of `__remove_mapping` in `mm/vmscan.c`. Based on the guidelines, I need to be careful not to include ubiquitous functions that will dilute the fuzzing effort. Things like `evict`, `__filemap_add_folio`, and `__remove_mapping` are off-limits because they are too common. My focus needs to be on specific feature logic and entrypoints. So, let's list the functions that I believe are the right candidates. In `mm/memfd_luo.c`, I'm looking at `memfd_luo_preserve`, `memfd_luo_unpreserve`, `memfd_luo_preserve_folios`, and `memfd_luo_migrate_folio`. In `mm/shmem.c`, `shmem_fallocate`, `shmem_setattr`, `shmem_add_to_page_cache`, and `shmem_writeout`. In `mm/truncate.c`, I have `truncate_inode_folio`, `truncate_inode_pages_range`, and `folio_unmap_invalidate`. I also have `folio_check_splittable` in `mm/huge_memory.c`, and `folio_migrate_mapping` and `migrate_huge_page_move_mapping` in `mm/migrate.c`. I then needed to verify these functions are valid symbols in the kernel source. I double-checked each one in the source code to be absolutely certain. The checks confirmed the symbols were correct. I also reviewed the relevant configuration options: `LIVEUPDATE`, `LIVEUPDATE_MEMFD`, `KEXEC_HANDOVER`, `KEXEC_HANDOVER_ENABLE_DEFAULT`, `MEMFD_CREATE`, `SHMEM`, and `TRANSPARENT_HUGEPAGE`. I recalled that the 'CONFIG_' prefix must be stripped when setting symbols. Finally, I considered the patch at a high level. The patch introduces `AS_FROZEN` to `struct address_space` to generalize the memfd frozen mapping mechanism. The patch enforces the `AS_FROZEN` state across different paths within the memory management subsystem. This includes page cache operations, migration, folio splitting, khugepaged collapse, shmem operations, inode operations, and truncation. The patch includes defensive assertions (`WARN_ON_ONCE` and `VM_WARN_ON_ONCE`) to ensure proper behavior. The `mm/memfd_luo.c` file is being rewritten to isolate folios and lock down page cache mapping transitions when preserving memfd files via live update sessions. Given the impact on core memory management, and the direct testability through memfd and liveupdate, I conclude that these identified functions are the correct symbols to guide fuzzing. |
| 56/2 | 2026/10/28 01:57 | tool | set-results |
0mArgs:{
"EnableConfigs": [
"LIVEUPDATE",
"LIVEUPDATE_MEMFD",
"KEXEC_HANDOVER",
"KEXEC_HANDOVER_ENABLE_DEFAULT",
"MEMFD_CREATE",
"SHMEM",
"TRANSPARENT_HUGEPAGE"
],
"FocusSymbols": [
"memfd_luo_preserve",
"memfd_luo_unpreserve",
"memfd_luo_preserve_folios",
"memfd_luo_migrate_folio",
"shmem_fallocate",
"shmem_setattr",
"shmem_add_to_page_cache",
"shmem_writeout",
"truncate_inode_folio",
"truncate_inode_pages_range",
"folio_unmap_invalidate",
"folio_check_splittable",
"folio_migrate_mapping",
"migrate_huge_page_move_mapping"
],
"Reasoning": "The patch series introduces a generalized address space frozen state (AS_FROZEN) to disallow modifying folios in frozen mappings, replacing a shmem-specific flag. It enforces this invariant across core memory management, page cache, truncation, migration, THP splitting, khugepaged collapse, and shmem operations. Crucially, it introduces multiple new assertions (WARN_ON_ONCE in evict(), truncate_inode_pages_range(), and shmem_undo_range(), as well as VM_WARN_ON_ONCE checks in filemap.c) to enforce mapping invariants. Furthermore, it completely refactors folio preservation and folio migration in mm/memfd_luo.c. Because these modifications impact core MM/VFS subsystems and add new invariants reachable via memfd operations and the liveupdate ioctl interface, fuzzing is strongly warranted.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": [
"LIVEUPDATE",
"LIVEUPDATE_MEMFD",
"KEXEC_HANDOVER",
"KEXEC_HANDOVER_ENABLE_DEFAULT",
"MEMFD_CREATE",
"SHMEM",
"TRANSPARENT_HUGEPAGE"
],
"FocusSymbols": [
"memfd_luo_preserve",
"memfd_luo_unpreserve",
"memfd_luo_preserve_folios",
"memfd_luo_migrate_folio",
"shmem_fallocate",
"shmem_setattr",
"shmem_add_to_page_cache",
"shmem_writeout",
"truncate_inode_folio",
"truncate_inode_pages_range",
"folio_unmap_invalidate",
"folio_check_splittable",
"folio_migrate_mapping",
"migrate_huge_page_move_mapping"
],
"Reasoning": "The patch series introduces a generalized address space frozen state (AS_FROZEN) to disallow modifying folios in frozen mappings, replacing a shmem-specific flag. It enforces this invariant across core memory management, page cache, truncation, migration, THP splitting, khugepaged collapse, and shmem operations. Crucially, it introduces multiple new assertions (WARN_ON_ONCE in evict(), truncate_inode_pages_range(), and shmem_undo_range(), as well as VM_WARN_ON_ONCE checks in filemap.c) to enforce mapping invariants. Furthermore, it completely refactors folio preservation and folio migration in mm/memfd_luo.c. Because these modifications impact core MM/VFS subsystems and add new invariants reachable via memfd operations and the liveupdate ioctl interface, fuzzing is strongly warranted.",
"WorthFuzzing": true
} |
| 57/1 | 2026/10/28 01:57 | action | If |
28mArgs:{
"WorthFuzzing": true
}Results: null |
| 58/2 | 2026/10/28 01:57 | agent | kmsan-evaluator |
28mModel:core Args: null Results: {
"KMSANReasoning": "The patch series introduces a generic address_space flag (AS_FROZEN) to prevent modifications to the page cache (folio addition, deletion, migration, splitting, collapsing, truncation) and refactors folio preservation in mm/memfd_luo.c for live updates across kexec.\n\nAnalysis of sanitizers:\n1. KMSAN applicability:\n- The patch does not expose any uninitialized memory to user space via copy_to_user, put_user, netlink, ioctl, or socket interfaces.\n- The structures modified/added (such as struct memfd_luo_folio_ser and struct migration_target_control) are fully initialized before use. The serialization array folios_ser has every element populated sequentially with all fields (pfn, flags, index) set, and all subsequent iterations and cleanup operations strictly bound access to the initialized count (nr_folios).\n- Adding checks for mapping_frozen() simply causes page cache operations (such as write_begin, split, collapse, migrate, remove) to safely fail early with -EBUSY or SCAN_FAIL. No conditional logic branches on uninitialized memory, nor does it allow reading uninitialized bytes from existing buffers.\n\n2. KASAN and other debugging tools:\n- The risks introduced by this patch involve concurrency and synchronization (lock ordering between i_pages xa_lock and inode locks), page cache state invariants, folio migration logic, and folio reference counting (isolating, pinning, and putting folios).\n- These bugs (such as deadlocks, refcounting leaks, use-after-free, or invalid memory accesses) are fully covered by standard KASAN, LOCKDEP, and kernel page asserts (VM_BUG_ON_FOLIO / VM_WARN_ON_ONCE).\n\nTherefore, a dedicated KMSAN fuzzing session is not justified.",
"NeedsKMSAN": false
}Instruction: You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.
CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
a comprehensive suite of debugging tools and sanitizers, including KASAN
(out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
(locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
or page allocations) and kernel-to-user memory info-leaks.
Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.
Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.
Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
attributes, ioctl output arguments, socket options, or BPF buffers) where fields
or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
uninitialized bytes of existing buffers.
Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
dereferences, locking deadlocks, or use-after-free bugs (these are already caught
by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.
Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit d3dd9b6fca9a06703893cd89e47456874917efa8
Author: syz-cluster <triage@syzkaller.com>
Date: Wed Oct 28 01:44:06 2026 +0000
syz-cluster: applied patch under review
diff --git a/fs/inode.c b/fs/inode.c
index a9d37be390a173..635083c42419fc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -7,6 +7,7 @@
#include <linux/fs.h>
#include <linux/filelock.h>
#include <linux/mm.h>
+#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/hash.h>
#include <linux/swap.h>
@@ -818,6 +819,14 @@ static void evict(struct inode *inode)
inode_wait_for_writeback(inode);
spin_unlock(&inode->i_lock);
+ /*
+ * Whoever froze the mapping must hold an inode reference until it is
+ * unfrozen, so this should never happen. If it does, unfreeze it so
+ * the final truncate does not leak folios.
+ */
+ if (WARN_ON_ONCE(mapping_frozen(&inode->i_data)))
+ clear_bit(AS_FROZEN, &inode->i_data.flags);
+
if (op->evict_inode) {
op->evict_inode(inode);
} else {
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 73af18a3736706..9b9d0459f39922 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -209,6 +209,7 @@ enum mapping_flags {
AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9,
AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't
account usage to user cgroups */
+ AS_FROZEN = 11, /* index -> folio mapping must not change */
/* Bits 16-25 are used for FOLIO_ORDER */
AS_FOLIO_ORDER_BITS = 5,
AS_FOLIO_ORDER_MIN = 16,
@@ -344,6 +345,40 @@ static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct addres
return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
}
+/*
+ * A frozen mapping disallows any change to its i_pages: no folio can be added,
+ * removed, replaced (migration, swap out), split, or collapsed.
+ *
+ * Only the page cache is frozen, not the file. Operations that need to change
+ * the page cache fail with -EBUSY, e.g. a write or fault that needs to allocate
+ * a new folio. Others, like reading or writing (to pages already in i_pages),
+ * still work.
+ *
+ * Locking: the flag is flipped under the i_pages lock. The filesystem must
+ * ensure mapping_set_frozen() doesn't race with a truncate or fallocate, since
+ * those can fail if frozen mid-way.
+ *
+ * The mapping must be unfrozen before the inode is evicted.
+ */
+static inline void mapping_set_frozen(struct address_space *mapping)
+{
+ xa_lock_irq(&mapping->i_pages);
+ set_bit(AS_FROZEN, &mapping->flags);
+ xa_unlock_irq(&mapping->i_pages);
+}
+
+static inline void mapping_clear_frozen(struct address_space *mapping)
+{
+ xa_lock_irq(&mapping->i_pages);
+ clear_bit(AS_FROZEN, &mapping->flags);
+ xa_unlock_irq(&mapping->i_pages);
+}
+
+static inline bool mapping_frozen(const struct address_space *mapping)
+{
+ return test_bit(AS_FROZEN, &mapping->flags);
+}
+
static inline gfp_t mapping_gfp_mask(const struct address_space *mapping)
{
return mapping->gfp_mask;
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index a7c7a96a7cbf90..5b48598a7b9523 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -23,14 +23,6 @@
#define SHMEM_F_NORESERVE BIT(0)
/* Disallow swapping. */
#define SHMEM_F_LOCKED BIT(1)
-/*
- * Disallow growing, shrinking, or hole punching in the inode. Combined with
- * folio pinning, makes sure the inode's mapping stays fixed.
- *
- * In some ways similar to F_SEAL_GROW | F_SEAL_SHRINK, but can be removed and
- * isn't directly visible to userspace.
- */
-#define SHMEM_F_MAPPING_FROZEN BIT(2)
struct shmem_inode_info {
spinlock_t lock;
@@ -202,15 +194,6 @@ static inline bool shmem_file(struct file *file)
return shmem_mapping(file->f_mapping);
}
-/* Must be called with inode lock taken exclusive. */
-static inline void shmem_freeze(struct inode *inode, bool freeze)
-{
- if (freeze)
- SHMEM_I(inode)->flags |= SHMEM_F_MAPPING_FROZEN;
- else
- SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN;
-}
-
/*
* If fallocate(FALLOC_FL_KEEP_SIZE) has been used, there may be pages
* beyond i_size's notion of EOF, which fallocate has committed to reserving:
diff --git a/mm/filemap.c b/mm/filemap.c
index b74bc1e5015c6f..d040c69177f792 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -138,6 +138,7 @@ static void page_cache_delete(struct address_space *mapping,
nr = folio_nr_pages(folio);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ VM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), folio);
xas_store(&xas, shadow);
xas_init_marks(&xas);
@@ -284,6 +285,7 @@ static void page_cache_delete_batch(struct address_space *mapping,
int i = 0;
struct folio *folio;
+ VM_WARN_ON_ONCE(mapping_frozen(mapping));
mapping_set_update(&xas, mapping);
xas_for_each(&xas, folio, ULONG_MAX) {
if (i >= folio_batch_count(fbatch))
@@ -826,6 +828,7 @@ void replace_page_cache_folio(struct folio *old, struct folio *new)
mem_cgroup_replace_folio(old, new);
xas_lock_irq(&xas);
+ VM_WARN_ON_ONCE_FOLIO(mapping_frozen(mapping), old);
xas_store(&xas, new);
old->mapping = NULL;
@@ -873,6 +876,10 @@ noinline int __filemap_add_folio(struct address_space *mapping,
void *entry, *old = NULL;
xas_lock_irq(&xas);
+ if (unlikely(mapping_frozen(mapping))) {
+ xas_set_err(&xas, -EBUSY);
+ goto unlock;
+ }
xas_for_each_conflict(&xas, entry) {
old = entry;
if (!xa_is_value(entry)) {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bd44d58e86845c..06d2f71ec74981 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3948,6 +3948,10 @@ int folio_check_splittable(struct folio *folio, unsigned int new_order,
if (!folio->mapping && !is_anon)
return -EBUSY;
+ /* Splitting would change a frozen mapping. */
+ if (!folio_test_anon(folio) && mapping_frozen(folio->mapping))
+ return -EBUSY;
+
/* order-1 is not supported for anonymous THP. */
if (is_anon && new_order == 1)
return -EINVAL;
@@ -4186,6 +4190,12 @@ static int __folio_freeze_split_file(struct folio *folio,
xas_lock_irq(&xas);
+ /* Can't change a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ ret = -EBUSY;
+ goto fail;
+ }
+
/*
* Check if the folio is present in page cache.
* We assume all tail are present too, if folio is there.
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index da91762f6358f2..5c78573f57c473 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2531,6 +2531,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
i_mmap_lock_read(mapping);
xas_lock_irq(&xas);
+ /* Can't collapse folios in a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ result = SCAN_FAIL;
+ goto immap_locked;
+ }
+
xas_set(&xas, start);
for (index = start; index < end; index++) {
if (!xas_next(&xas)) {
@@ -2582,6 +2588,12 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
}
} else {
xas_lock_irq(&xas);
+ /* Can't collapse folios in a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ xas_unlock_irq(&xas);
+ result = SCAN_FAIL;
+ goto rollback;
+ }
}
if (is_shmem) {
diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index 59de210bee5f9e..ec5abd41ecb8ba 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -77,26 +77,127 @@
#include <linux/kexec_handover.h>
#include <linux/kho/abi/memfd.h>
#include <linux/liveupdate.h>
+#include <linux/migrate.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/signal.h>
#include <linux/shmem_fs.h>
+#include <linux/swap.h>
#include <linux/vmalloc.h>
#include <linux/memfd.h>
+#include <linux/pagemap.h>
#include <uapi/linux/memfd.h>
#include "internal.h"
+static void memfd_luo_put_folios(const struct memfd_luo_folio_ser *folios_ser,
+ u64 nr_folios)
+{
+ u64 i;
+
+ for (i = 0; i < nr_folios; i++) {
+ const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+ struct folio *folio;
+
+ if (!pfolio->pfn)
+ continue;
+
+ folio = pfn_folio(pfolio->pfn);
+
+ kho_unpreserve_folio(folio);
+ folio_put(folio);
+ }
+}
+
+/* How many times to retry isolating a folio someone else has isolated. */
+#define MEMFD_LUO_MIGRATE_RETRIES 3
+
+/*
+ * Move a folio out of ZONE_MOVABLE or CMA, so it can be held until the next
+ * kernel. Called with a reference on the unlocked folio, which is always
+ * dropped. The caller must look up the folio again afterwards.
+ *
+ * Returns 0 on success, -EBUSY if the folio could not be isolated (e.g.
+ * because someone else has it isolated right now), or -ENOMEM if migration
+ * failed.
+ */
+static int memfd_luo_migrate_folio(struct folio *folio)
+{
+ struct migration_target_control mtc = {
+ .nid = NUMA_NO_NODE,
+ /* Not movable, so the target is neither in ZONE_MOVABLE nor CMA. */
+ .gfp_mask = GFP_USER | __GFP_NOWARN,
+ .reason = MR_LONGTERM_PIN,
+ };
+ LIST_HEAD(source);
+ bool isolated;
+
+ /* Flush per-CPU LRU batches holding the folio so isolation works. */
+ lru_cache_drain_for_folio(folio, 1, NULL);
+ isolated = isolate_folio_to_list(folio, &source);
+ /* Isolation holds its own reference. */
+ folio_put(folio);
+ if (!isolated)
+ return -EBUSY;
+
+ if (migrate_pages(&source, alloc_migration_target, NULL,
+ (unsigned long)&mtc, MIGRATE_SYNC, MR_LONGTERM_PIN,
+ NULL)) {
+ putback_movable_pages(&source);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static int memfd_luo_preserve_folio(struct folio *folio,
+ struct memfd_luo_folio_ser *pfolio)
+{
+ int err;
+
+ err = kho_preserve_folio(folio);
+ if (err)
+ return err;
+
+ /*
+ * A dirty folio is one which has been written to. A clean folio
+ * is its opposite. Since a clean folio does not carry user
+ * data, it can be freed by page reclaim under memory pressure.
+ *
+ * Saving the dirty flag at prepare() time doesn't work since it
+ * can change later. Saving it at freeze() also won't work
+ * because the dirty bit is normally synced at unmap and there
+ * might still be a mapping of the file at freeze().
+ *
+ * To see why this is a problem, say a folio is clean at
+ * preserve, but gets dirtied later. The pfolio flags will mark
+ * it as clean. After retrieve, the next kernel might try to
+ * reclaim this folio under memory pressure, losing user data.
+ *
+ * Unconditionally mark it dirty to avoid this problem. This
+ * comes at the cost of making clean folios un-reclaimable after
+ * live update.
+ */
+ folio_mark_dirty(folio);
+
+ pfolio->pfn = folio_pfn(folio);
+ pfolio->flags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;
+ pfolio->index = folio->index;
+
+ return 0;
+}
+
static int memfd_luo_preserve_folios(struct file *file,
struct kho_vmalloc *kho_vmalloc,
struct memfd_luo_folio_ser **out_folios_ser,
u64 *nr_foliosp)
{
+ struct memfd_luo_folio_ser *folios_ser, *shrunk;
struct inode *inode = file_inode(file);
- struct memfd_luo_folio_ser *folios_ser;
- unsigned int max_folios;
- long i, size, nr_pinned;
- struct folio **folios;
- int err = -EINVAL;
- pgoff_t offset;
- u64 nr_folios;
+ u64 nr_folios = 0, max_folios;
+ int err, busy_retries = 0;
+ unsigned int pin_flags;
+ pgoff_t index = 0, end;
+ loff_t size;
size = i_size_read(inode);
/*
@@ -113,99 +214,77 @@ static int memfd_luo_preserve_folios(struct file *file,
* Guess the number of folios based on inode size. Real number might end
* up being smaller if there are higher order folios.
*/
- max_folios = PAGE_ALIGN(size) / PAGE_SIZE;
- folios = kvmalloc_objs(*folios, max_folios);
- if (!folios)
+ end = DIV_ROUND_UP_ULL(size, PAGE_SIZE);
+ max_folios = end;
+ folios_ser = vmalloc_array(max_folios, sizeof(*folios_ser));
+ if (!folios_ser)
return -ENOMEM;
/*
- * Pin the folios so they don't move around behind our back. This also
- * ensures none of the folios are in CMA -- which ensures they don't
- * fall in KHO scratch memory. It also moves swapped out folios back to
- * memory.
+ * The folios are held until the next kernel, so keep newly allocated
+ * ones out of ZONE_MOVABLE and CMA -- which also ensures they don't
+ * fall in KHO bootmem. Existing ones are migrated below.
*
- * A side effect of doing this is that it allocates a folio for all
- * indices in the file. This might waste memory on sparse memfds. If
- * that is really a problem in the future, we can have a
- * memfd_pin_folios() variant that does not allocate a page on empty
- * slots.
+ * A side effect of this is that it allocates a folio for all indices in
+ * the file. This might waste memory on sparse memfds. If that is really
+ * a problem in the future, this loop can be taught to skip empty slots.
*/
- nr_pinned = memfd_pin_folios(file, 0, size - 1, folios, max_folios,
- &offset);
- if (nr_pinned < 0) {
- err = nr_pinned;
- pr_err("failed to pin folios: %d\n", err);
- goto err_free_folios;
- }
- nr_folios = nr_pinned;
+ pin_flags = memalloc_pin_save();
+ while (index < end) {
+ struct folio *folio;
- folios_ser = vcalloc(nr_folios, sizeof(*folios_ser));
- if (!folios_ser) {
- err = -ENOMEM;
- goto err_unpin;
- }
+ cond_resched();
- for (i = 0; i < nr_folios; i++) {
- struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
- struct folio *folio = folios[i];
+ if (fatal_signal_pending(current)) {
+ err = -EINTR;
+ goto err_restore;
+ }
+
+ if (WARN_ON_ONCE(nr_folios >= max_folios)) {
+ err = -EINVAL;
+ goto err_restore;
+ }
- err = kho_preserve_folio(folio);
+ err = shmem_get_folio(inode, index, 0, &folio, SGP_CACHE);
if (err)
- goto err_unpreserve;
-
- folio_lock(folio);
-
- /*
- * A dirty folio is one which has been written to. A clean folio
- * is its opposite. Since a clean folio does not carry user
- * data, it can be freed by page reclaim under memory pressure.
- *
- * Saving the dirty flag at prepare() time doesn't work since it
- * can change later. Saving it at freeze() also won't work
- * because the dirty bit is normally synced at unmap and there
- * might still be a mapping of the file at freeze().
- *
- * To see why this is a problem, say a folio is clean at
- * preserve, but gets dirtied later. The pfolio flags will mark
- * it as clean. After retrieve, the next kernel might try to
- * reclaim this folio under memory pressure, losing user data.
- *
- * Unconditionally mark it dirty to avoid this problem. This
- * comes at the cost of making clean folios un-reclaimable after
- * live update.
- */
- folio_mark_dirty(folio);
-
- /*
- * If the folio is not uptodate, it was fallocated but never
- * used. Saving this flag at prepare() doesn't work since it
- * might change later when someone uses the folio.
- *
- * Since we have taken the performance penalty of allocating,
- * zeroing, and pinning all the folios in the holes, take a bit
- * more and zero all non-uptodate folios too.
- *
- * NOTE: For someone looking to improve preserve performance,
- * this is a good place to look.
- */
- if (!folio_test_uptodate(folio)) {
- folio_zero_range(folio, 0, folio_size(folio));
- flush_dcache_folio(folio);
- folio_mark_uptodate(folio);
+ goto err_restore;
+
+ if (unlikely(!folio_is_longterm_pinnable(folio))) {
+ folio_unlock(folio);
+ err = memfd_luo_migrate_folio(folio);
+ /* Someone else might have it isolated, retry a bit. */
+ if (err == -EBUSY && ++busy_retries < MEMFD_LUO_MIGRATE_RETRIES)
+ continue;
+ if (err)
+ goto err_restore;
+ continue;
}
+ err = memfd_luo_preserve_folio(folio, &folios_ser[nr_folios]);
+ index = folio_next_index(folio);
folio_unlock(folio);
-
- pfolio->pfn = folio_pfn(folio);
- pfolio->flags = MEMFD_LUO_FOLIO_DIRTY | MEMFD_LUO_FOLIO_UPTODATE;
- pfolio->index = folio->index;
+ if (err) {
+ folio_put(folio);
+ goto err_restore;
+ }
+ nr_folios++;
+ busy_retries = 0;
}
+ memalloc_pin_restore(pin_flags);
+
+ /*
+ * Free the unused tail so it doesn't get preserved. If vrealloc fails,
+ * the folios_ser is still valid.
+ */
+ shrunk = vrealloc(folios_ser, array_size(nr_folios, sizeof(*folios_ser)),
+ GFP_KERNEL);
+ if (shrunk)
+ folios_ser = shrunk;
err = kho_preserve_vmalloc(folios_ser, kho_vmalloc);
if (err)
- goto err_unpreserve;
+ goto err_put;
- kvfree(folios);
*nr_foliosp = nr_folios;
*out_folios_ser = folios_ser;
@@ -216,15 +295,11 @@ static int memfd_luo_preserve_folios(struct file *file,
*/
return 0;
-err_unpreserve:
- for (i = i - 1; i >= 0; i--)
- kho_unpreserve_folio(folios[i]);
+err_restore:
+ memalloc_pin_restore(pin_flags);
+err_put:
+ memfd_luo_put_folios(folios_ser, nr_folios);
vfree(folios_ser);
-err_unpin:
- unpin_folios(folios, nr_folios);
-err_free_folios:
- kvfree(folios);
-
return err;
}
@@ -232,26 +307,11 @@ static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,
struct memfd_luo_folio_ser *folios_ser,
u64 nr_folios)
{
- long i;
-
if (!nr_folios)
return;
kho_unpreserve_vmalloc(kho_vmalloc);
-
- for (i = 0; i < nr_folios; i++) {
- const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
- struct folio *folio;
-
- if (!pfolio->pfn)
- continue;
-
- folio = pfn_folio(pfolio->pfn);
-
- kho_unpreserve_folio(folio);
- unpin_folio(folio);
- }
-
+ memfd_luo_put_folios(folios_ser, nr_folios);
vfree(folios_ser);
}
@@ -264,7 +324,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
int err = 0, seals;
inode_lock(inode);
- shmem_freeze(inode, true);
/* Allocate the main serialization structure in preserved memory */
ser = kho_alloc_preserve(sizeof(*ser));
@@ -288,15 +347,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
ser->pos = args->file->f_pos;
inode_size = i_size_read(inode);
- /*
- * memfd_pin_folios() caps at UINT_MAX folios; refuse larger
- * files to avoid silently preserving only a prefix.
- */
- if (DIV_ROUND_UP_ULL(inode_size, PAGE_SIZE) > UINT_MAX) {
- err = -EFBIG;
- goto err_free_ser;
- }
-
ser->size = inode_size;
ser->seals = seals;
@@ -305,6 +355,12 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
if (err)
goto err_free_ser;
+ /*
+ * All the folios in the file are now stable. Freeze the mapping to make
+ * sure new ones can't be added.
+ */
+ mapping_set_frozen(inode->i_mapping);
+
ser->nr_folios = nr_folios;
inode_unlock(inode);
@@ -316,7 +372,6 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
err_free_ser:
kho_unpreserve_free(ser);
err_unlock:
- shmem_freeze(inode, false);
inode_unlock(inode);
return err;
}
@@ -348,7 +403,7 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
return;
inode_lock(inode);
- shmem_freeze(inode, false);
+ mapping_clear_frozen(inode->i_mapping);
ser = phys_to_virt(args->serialized_data);
diff --git a/mm/migrate.c b/mm/migrate.c
index d649a6cfce6c09..6ce01871d72e39 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -614,10 +614,16 @@ static int __folio_migrate_mapping(struct address_space *mapping,
oldzone = folio_zone(folio);
newzone = folio_zone(newfolio);
- if (folio_test_swapcache(folio))
+ if (folio_test_swapcache(folio)) {
ci = swap_cluster_get_and_lock_irq(folio);
- else
+ } else {
xas_lock_irq(&xas);
+ /* Can't replace folios in a frozen mapping. */
+ if (mapping_frozen(mapping)) {
+ xas_unlock_irq(&xas);
+ return -EBUSY;
+ }
+ }
if (!folio_ref_freeze(folio, expected_count)) {
if (ci)
@@ -750,6 +756,10 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
return rc;
xas_lock_irq(&xas);
+ if (mapping_frozen(mapping)) {
+ xas_unlock_irq(&xas);
+ return -EBUSY;
+ }
if (!folio_ref_freeze(src, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
diff --git a/mm/shmem.c b/mm/shmem.c
index 13e0786436cda1..1c70fd306bec21 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1121,6 +1121,10 @@ int shmem_add_to_page_cache(struct folio *folio,
do {
iter = swap;
xas_lock_irq(&xas);
+ if (unlikely(mapping_frozen(mapping))) {
+ xas_set_err(&xas, -EBUSY);
+ goto unlock;
+ }
xas_for_each_conflict(&xas, entry) {
/*
* The range must either be empty, or filled with
@@ -1345,6 +1349,10 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
if (lend == -1)
end = -1; /* unsigned, so actually very big */
+ /* Callers must not try to truncate a frozen mapping. */
+ if (WARN_ON_ONCE(mapping_frozen(mapping)))
+ return;
+
if (info->fallocend > start && info->fallocend <= end && !unfalloc)
info->fallocend = start;
@@ -1562,8 +1570,6 @@ static int shmem_setattr(struct mnt_idmap *idmap,
return -EPERM;
if (newsize != oldsize) {
- if (info->flags & SHMEM_F_MAPPING_FROZEN)
- return -EPERM;
error = shmem_reacct_size(SHMEM_I(inode)->flags,
oldsize, newsize);
if (error)
@@ -1575,6 +1581,11 @@ static int shmem_setattr(struct mnt_idmap *idmap,
}
if (newsize <= oldsize) {
loff_t holebegin = round_up(newsize, PAGE_SIZE);
+
+ /* No truncation allowed on a frozen mapping. */
+ if (mapping_frozen(inode->i_mapping))
+ return -EBUSY;
+
if (oldsize > holebegin)
unmap_mapping_range(inode->i_mapping,
holebegin, 0, 1);
@@ -1822,6 +1833,10 @@ int shmem_writeout(struct swap_io_ctx *ctx, struct folio *folio,
if ((info->flags & SHMEM_F_LOCKED) || sbinfo->noswap)
goto redirty;
+ /* Swapping out would replace the folio in a frozen mapping. */
+ if (mapping_frozen(mapping))
+ goto redirty;
+
if (!total_swap_pages)
goto redirty;
@@ -2483,6 +2498,13 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
if (softleaf_is_poison_marker(index_entry))
return -EIO;
+ /*
+ * Swapping in would change the i_pages of a frozen mapping. A frozen
+ * mapping should not have swap entries in the first place.
+ */
+ if (unlikely(mapping_frozen(mapping)))
+ return -EBUSY;
+
si = get_swap_device(index_entry);
order = shmem_confirm_swap(mapping, index, index_entry);
if (IS_ERR_OR_NULL(si)) {
@@ -3463,10 +3485,6 @@ shmem_write_begin(const struct kiocb *iocb, struct address_space *mapping,
return -EPERM;
}
- if (unlikely((info->flags & SHMEM_F_MAPPING_FROZEN) &&
- pos + len > inode->i_size))
- return -EPERM;
-
ret = shmem_get_folio(inode, index, pos + len, &folio, SGP_WRITE);
if (ret)
return ret;
@@ -3841,8 +3859,8 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
inode_lock(inode);
- if (info->flags & SHMEM_F_MAPPING_FROZEN) {
- error = -EPERM;
+ if (mapping_frozen(inode->i_mapping)) {
+ error = -EBUSY;
goto out;
}
diff --git a/mm/truncate.c b/mm/truncate.c
index 733d2713a875a5..6512f460a28e94 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -171,6 +171,8 @@ int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
{
if (folio->mapping != mapping)
return -EIO;
+ if (mapping_frozen(mapping))
+ return -EBUSY;
truncate_cleanup_folio(folio);
filemap_remove_folio(folio);
@@ -367,6 +369,8 @@ long mapping_evict_folio(struct address_space *mapping, struct folio *folio)
return 0;
if (folio_test_dirty(folio) || folio_test_writeback(folio))
return 0;
+ if (mapping_frozen(mapping))
+ return 0;
/* The refcount will be elevated if any page in the folio is mapped */
if (folio_ref_count(folio) >
folio_nr_pages(folio) + folio_has_private(folio) + 1)
@@ -419,6 +423,13 @@ void truncate_inode_pages_range(struct address_space *mapping,
if (mapping_empty(mapping))
return;
+ /*
+ * Callers must not try to truncate a frozen mapping. Filesystems that
+ * support frozen mappings must refuse shrinking and hole punching
+ * before getting here.
+ */
+ if (WARN_ON_ONCE(mapping_frozen(mapping)))
+ return;
/*
* 'start' and 'end' always covers the range of folios to be fully
* truncated, with both boundaries aligned inwards to 1 << min_order.
@@ -668,6 +679,9 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ if (mapping_frozen(mapping))
+ return -EBUSY;
+
if (folio_mapped(folio))
unmap_mapping_folio(folio);
BUG_ON(folio_mapped(folio));
@@ -682,7 +696,7 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
- if (folio_test_dirty(folio))
+ if (folio_test_dirty(folio) || mapping_frozen(mapping))
goto failed;
BUG_ON(folio_has_private(folio));
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9959ca158ce835..86ef233e8752ee 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -766,6 +766,9 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
} else {
spin_lock(&mapping->host->i_lock);
xa_lock_irq(&mapping->i_pages);
+ /* Can't remove folios from a frozen mapping. */
+ if (mapping_frozen(mapping))
+ goto cannot_free;
}
/*
|
| 59/3 | 2026/10/28 01:57 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 11867 output: 19 thoughts: 1036 Thoughts: **KMSAN Evaluation: Patch Series Analysis** Alright, let's dive into this patch series. My initial thought is to determine if these code changes warrant a dedicated KMSAN fuzzing session, in addition to our standard KASAN efforts. As an expert, I know the drill: KASAN nails out-of-bounds accesses, UAFs, double frees, and such. KMSAN, on the other hand, is the go-to tool for uninitialized memory reads—stuff slipping through the cracks on the stack, heap, or during page allocations, plus any potential kernel-to-user memory leaks. My rule of thumb is straightforward: If KASAN, LOCKDEP, or any other standard detector can catch a bug, there's no need to spin up a KMSAN session. The logic is, we set `NeedsKMSAN=true` only if we see kernel structures being passed to user space (via `copy_to_user`, `put_user`, netlink attributes, ioctl output, socket options, BPF buffers) where fields *might* be uninitialized. Also, if there's conditional logic that relies on uninitialized variables or struct fields, KMSAN gets the nod. Allocation of complex data structures where uninitialized fields could be read later is another red flag. Finally, if the patch introduces new bounds checks, lengths, or logic that *could* lead to accessing uninitialized bytes, then KMSAN is needed. Conversely, if the patch is mainly about preventing out-of-bounds access, array overflows, null dereferences, locking issues, or UAFs, we stick with the standard detectors. If everything's zeroed or initialized before being read or copied, we're good. If the patch doesn't introduce any risk of uninitialized memory usage or info-leaks, then KMSAN is not needed. Now, let's scrutinize the patch. It touches `fs/inode.c`, `include/linux/pagemap.h`, `include/linux/shmem_fs.h`, and quite a few files in `mm/`: `filemap.c`, `huge_memory.c`, `khugepaged.c`, `memfd_luo.c`, `migrate.c`, `shmem.c`, `truncate.c`, and `vmscan.c`. It looks like a mapping freeze/unfreeze mechanism is the key change. We see checks for `mapping_frozen` sprinkled throughout. Hold on a second... wait... `memfd_luo.c` is the most interesting one! Let's drill down into that file. We're replacing `shmem_freeze()` and working with `mapping_set_frozen(inode->i_mapping)`. A major part of the work is dealing with folio preservation in `memfd_luo`, and there's a loop that's been explicitly written to use `shmem_get_folio` and a new `memfd_luo_preserve_folio` function. Additionally, there is allocation/reallocation of `folios_ser` with `vmalloc_array`. Aha! Now things are getting interesting. My spidey senses are tingling. I know that `vmalloc_array` *does not* zero the memory! I have to double check myself here to be sure, since this is a critical component of the logic. Is this a potential KMSAN trigger? It looks like we have a strong candidate for a KMSAN session! I need to investigate `memfd_luo_preserve_folio` and the associated functions closely. |
| 60/3 | 2026/10/28 01:59 | tool | grepper |
0mArgs:{
"Expression": "define vmalloc_array"
}Results: {
"Output": "include/linux/vmalloc.h=197=extern void *vmalloc_array_noprof(size_t n, size_t size) __alloc_size(1, 2);\ninclude/linux/vmalloc.h:198:#define vmalloc_array(...)\talloc_hooks(vmalloc_array_noprof(__VA_ARGS__))\ninclude/linux/vmalloc.h-199-\n"
} |
| 61/3 | 2026/10/28 02:00 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 13789 output: 22 thoughts: 24 Thoughts: Okay, let's dive into this. Here's my thought process on dissecting the `vmalloc_array_noprof` implementation in `mm/vmalloc.c`: **Dissecting `vmalloc_array_noprof`** Alright, I need to get a handle on what this function is doing. `vmalloc_array_noprof`... sounds like a vmalloc-related function with some specific constraints. The "array" part suggests it's likely allocating a contiguous block, or perhaps simulating one, for an array of some sort. The "noprof" suffix is particularly interesting. That strongly indicates this allocation is explicitly *not* meant to be profiled, which implies a potential performance-sensitive region where profiling overhead would be a problem, or it might be used in a critical path where profiling could lead to issues, like a race condition or deadlock. I'll head straight for `mm/vmalloc.c` and start digging through the code. I'm expecting to find the standard vmalloc machinery at play here: likely a call to `vm_alloc` or similar, some page mapping and initialization, and then potentially some locking mechanisms to protect against race conditions. Given the "noprof" aspect, I'll be particularly watchful for any conditional profiling code that's been explicitly disabled. I'll need to understand where this function is called from to grasp the bigger picture, too. Why is profiling specifically undesirable here? Are we talking about a really high-frequency allocation that's affecting a tight loop? Or maybe this allocation is done really early in the boot process? It's all clues to put together. |
| 62/3 | 2026/10/28 02:00 | tool | grepper |
0mArgs:{
"Expression": "vmalloc_array_noprof"
}Results: {
"Output": "include/linux/ptr_ring.h=499=static inline void **__ptr_ring_init_queue_alloc_noprof(unsigned int size, gfp_t gfp)\n--\ninclude/linux/ptr_ring.h-502-\t\treturn NULL;\ninclude/linux/ptr_ring.h:503:\treturn kvmalloc_array_noprof(size, sizeof(void *), gfp | __GFP_ZERO);\ninclude/linux/ptr_ring.h-504-}\n--\ninclude/linux/slab.h=1367=_kvmalloc_array_node_noprof(size_t n, size_t size, gfp_t flags, int node, kmalloc_token_t token)\n--\ninclude/linux/slab.h-1376-#define kvmalloc_array_node_noprof(...)\t\t_kvmalloc_array_node_noprof(__VA_ARGS__, __kmalloc_token(__VA_ARGS__))\ninclude/linux/slab.h:1377:#define kvmalloc_array_noprof(...)\t\tkvmalloc_array_node_noprof(__VA_ARGS__, NUMA_NO_NODE)\ninclude/linux/slab.h-1378-#define kvcalloc_node_noprof(_n,_s,_f,_node)\tkvmalloc_array_node_noprof(_n,_s,(_f)|__GFP_ZERO,_node)\n--\ninclude/linux/slab.h-1380-\ninclude/linux/slab.h:1381:#define kvmalloc_array(...)\t\t\talloc_hooks(kvmalloc_array_noprof(__VA_ARGS__))\ninclude/linux/slab.h-1382-#define kvcalloc_node(...)\t\t\talloc_hooks(kvcalloc_node_noprof(__VA_ARGS__))\n--\ninclude/linux/vmalloc.h=189=static inline void *vmalloc_huge(unsigned long size, gfp_t gfp_mask)\n--\ninclude/linux/vmalloc.h-193-\ninclude/linux/vmalloc.h:194:extern void *__vmalloc_array_noprof(size_t n, size_t size, gfp_t flags) __alloc_size(1, 2);\ninclude/linux/vmalloc.h:195:#define __vmalloc_array(...)\talloc_hooks(__vmalloc_array_noprof(__VA_ARGS__))\ninclude/linux/vmalloc.h-196-\ninclude/linux/vmalloc.h:197:extern void *vmalloc_array_noprof(size_t n, size_t size) __alloc_size(1, 2);\ninclude/linux/vmalloc.h:198:#define vmalloc_array(...)\talloc_hooks(vmalloc_array_noprof(__VA_ARGS__))\ninclude/linux/vmalloc.h-199-\n--\nmm/util.c=627=unsigned long vm_mmap_shadow_stack(unsigned long addr, unsigned long len,\n--\nmm/util.c-655- */\nmm/util.c:656:void *__vmalloc_array_noprof(size_t n, size_t size, gfp_t flags)\nmm/util.c-657-{\n--\nmm/util.c-663-}\nmm/util.c:664:EXPORT_SYMBOL(__vmalloc_array_noprof);\nmm/util.c-665-\n--\nmm/util.c-670- */\nmm/util.c:671:void *vmalloc_array_noprof(size_t n, size_t size)\nmm/util.c-672-{\nmm/util.c:673:\treturn __vmalloc_array_noprof(n, size, GFP_KERNEL);\nmm/util.c-674-}\nmm/util.c:675:EXPORT_SYMBOL(vmalloc_array_noprof);\nmm/util.c-676-\n--\nmm/util.c=683=void *__vcalloc_noprof(size_t n, size_t size, gfp_t flags)\nmm/util.c-684-{\nmm/util.c:685:\treturn __vmalloc_array_noprof(n, size, flags | __GFP_ZERO);\nmm/util.c-686-}\n--\nmm/util.c=694=void *vcalloc_noprof(size_t n, size_t size)\nmm/util.c-695-{\nmm/util.c:696:\treturn __vmalloc_array_noprof(n, size, GFP_KERNEL | __GFP_ZERO);\nmm/util.c-697-}\n"
} |
| 63/3 | 2026/10/28 02:00 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 15350 output: 30 thoughts: 115 Thoughts: **Investigating Potential Zeroing Discrepancies in Kernel Memory Allocation** Okay, hold on a second! I need to carefully compare `vcalloc` with `vmalloc_array`. I noticed something potentially significant. Looking at `vcalloc`, the flags used include `__GFP_ZERO`. However, when I look at `vmalloc_array`, it's using just `GFP_KERNEL` and, critically, *doesn't* include `__GFP_ZERO`. This is a red flag! I need to quickly understand if `vmalloc`, the function underlying these array allocation helpers, is implicitly zeroing the allocated pages or not. Does `vmalloc` itself take care of zeroing pages? I need to check the low-level allocation behavior within `mm/vmalloc.c`. I'll delve into the implementations of `__vmalloc_noprof` and `__vmalloc_node_range_noprof` to see exactly how those functions allocate the pages for a `vmalloc` region. That should give me the answer I need. |
| 64/3 | 2026/10/28 02:00 | tool | grepper |
0mArgs:{
"Expression": "vmalloc\\(",
"PathPrefixes": [
"mm/vmalloc.c"
]
}Results: {
"Output": "mm/vmalloc.c=69=static bool __ro_after_init vmap_allow_huge = true;\nmm/vmalloc.c-70-\nmm/vmalloc.c:71:static int __init set_nohugevmalloc(char *str)\nmm/vmalloc.c-72-{\n--\nmm/vmalloc.c=802=int is_vmalloc_or_module_addr(const void *x)\n--\nmm/vmalloc.c-805-\t * ARM, x86-64 and sparc64 put modules in a special place,\nmm/vmalloc.c:806:\t * and fall back on vmalloc() if that fails. Others\nmm/vmalloc.c-807-\t * just put it in the vmalloc space.\n--\nmm/vmalloc.c=882=EXPORT_SYMBOL(vmalloc_to_page);\n--\nmm/vmalloc.c-884-/*\nmm/vmalloc.c:885: * Map a vmalloc()-space virtual address to the physical page frame number.\nmm/vmalloc.c-886- */\n--\nmm/vmalloc.c=2059=static struct vmap_area *alloc_vmap_area(unsigned long size,\n--\nmm/vmalloc.c-2114-\t\t * This is not a fast path. Check if yielding is needed. This\nmm/vmalloc.c:2115:\t\t * is the only reschedule point in the vmalloc() path.\nmm/vmalloc.c-2116-\t\t */\n--\nmm/vmalloc.c-2158-\nmm/vmalloc.c:2159:\tret = kasan_populate_vmalloc(addr, size, gfp_mask);\nmm/vmalloc.c-2160-\tif (ret) {\n--\nmm/vmalloc.c=2309=kasan_release_vmalloc_node(struct vmap_node *vn)\n--\nmm/vmalloc.c-2319-\t\tif (is_vmalloc_or_module_addr((void *) va-\u003eva_start))\nmm/vmalloc.c:2320:\t\t\tkasan_release_vmalloc(va-\u003eva_start, va-\u003eva_end,\nmm/vmalloc.c-2321-\t\t\t\tva-\u003eva_start, va-\u003eva_end,\n--\nmm/vmalloc.c-2329-\nmm/vmalloc.c:2330:\tkasan_release_vmalloc(start, end, start, end, KASAN_VMALLOC_TLB_FLUSH);\nmm/vmalloc.c-2331-}\n--\nmm/vmalloc.c=3087=void vm_unmap_ram(const void *mem, unsigned int count)\n--\nmm/vmalloc.c-3098-\nmm/vmalloc.c:3099:\tkasan_poison_vmalloc(mem, size);\nmm/vmalloc.c-3100-\n--\nmm/vmalloc.c=3130=void *vm_map_ram(struct page **pages, unsigned int count, int node)\n--\nmm/vmalloc.c-3162-\t * With hardware tag-based KASAN, marking is skipped for\nmm/vmalloc.c:3163:\t * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().\nmm/vmalloc.c-3164-\t */\nmm/vmalloc.c:3165:\tmem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_PROT_NORMAL);\nmm/vmalloc.c-3166-\n--\nmm/vmalloc.c=3265=struct vm_struct *__get_vm_area_node(unsigned long size,\n--\nmm/vmalloc.c-3311-\t * With hardware tag-based KASAN, marking is skipped for\nmm/vmalloc.c:3312:\t * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().\nmm/vmalloc.c-3313-\t */\nmm/vmalloc.c-3314-\tif (!(flags \u0026 VM_ALLOC))\nmm/vmalloc.c:3315:\t\tarea-\u003eaddr = kasan_unpoison_vmalloc(area-\u003eaddr, requested_size,\nmm/vmalloc.c-3316-\t\t\t\t\t\t KASAN_VMALLOC_PROT_NORMAL);\n--\nmm/vmalloc.c=3387=struct vm_struct *remove_vm_area(const void *addr)\n--\nmm/vmalloc.c-3405-\tkasan_free_module_shadow(vm);\nmm/vmalloc.c:3406:\tkasan_poison_vmalloc(vm-\u003eaddr, get_vm_area_size(vm));\nmm/vmalloc.c-3407-\n--\nmm/vmalloc.c=3464=static void delayed_vfree_work(struct work_struct *w)\n--\nmm/vmalloc.c-3473-/**\nmm/vmalloc.c:3474: * vfree_atomic - release memory allocated by vmalloc()\nmm/vmalloc.c-3475- * @addr:\t memory base address\n--\nmm/vmalloc.c=3508=static void vm_area_free_pages(struct vm_struct *vm, unsigned long start_idx,\n--\nmm/vmalloc.c-3523-/**\nmm/vmalloc.c:3524: * vfree - Release memory allocated by vmalloc()\nmm/vmalloc.c-3525- * @addr: Memory base address\n--\nmm/vmalloc.c-3527- * Free the virtually continuous memory area starting at @addr, as obtained\nmm/vmalloc.c:3528: * from one of the vmalloc() family of APIs. This will usually also free the\nmm/vmalloc.c-3529- * physical memory underlying the virtual allocation, but that memory is\n--\nmm/vmalloc.c=4034=static gfp_t vmalloc_fix_flags(gfp_t flags)\n--\nmm/vmalloc.c-4063- * Please note %GFP_ATOMIC and %GFP_NOWAIT are supported only\nmm/vmalloc.c:4064: * by __vmalloc().\nmm/vmalloc.c-4065- *\n--\nmm/vmalloc.c=4085=void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,\n--\nmm/vmalloc.c-4147-\t * Prepare arguments for __vmalloc_area_node() and\nmm/vmalloc.c:4148:\t * kasan_unpoison_vmalloc().\nmm/vmalloc.c-4149-\t */\n--\nmm/vmalloc.c-4160-\t\t\t * pages backing VM_ALLOC mapping. Memory is instead\nmm/vmalloc.c:4161:\t\t\t * poisoned and zeroed by kasan_unpoison_vmalloc().\nmm/vmalloc.c-4162-\t\t\t */\n--\nmm/vmalloc.c-4180-\t * Tag-based KASAN modes only assign tags to normal non-executable\nmm/vmalloc.c:4181:\t * allocations, see __kasan_unpoison_vmalloc().\nmm/vmalloc.c-4182-\t */\n--\nmm/vmalloc.c-4188-\tif (!skip_vmalloc_kasan)\nmm/vmalloc.c:4189:\t\tarea-\u003eaddr = kasan_unpoison_vmalloc(area-\u003eaddr, size, kasan_flags);\nmm/vmalloc.c-4190-\n--\nmm/vmalloc.c-4198-\tif (!(vm_flags \u0026 VM_DEFER_KMEMLEAK))\nmm/vmalloc.c:4199:\t\tkmemleak_vmalloc(area, PAGE_ALIGN(size), gfp_mask);\nmm/vmalloc.c-4200-\n--\nmm/vmalloc.c=4251=EXPORT_SYMBOL(__vmalloc_noprof);\n--\nmm/vmalloc.c-4260- * For tight control over page level allocator and protection flags\nmm/vmalloc.c:4261: * use __vmalloc() instead.\nmm/vmalloc.c-4262- *\n--\nmm/vmalloc.c=4293=EXPORT_SYMBOL_GPL(vmalloc_huge_node_noprof);\n--\nmm/vmalloc.c-4303- * For tight control over page level allocator and protection flags\nmm/vmalloc.c:4304: * use __vmalloc() instead.\nmm/vmalloc.c-4305- *\n--\nmm/vmalloc.c=4331=EXPORT_SYMBOL(vmalloc_user_noprof);\n--\nmm/vmalloc.c-4341- * For tight control over page level allocator and protection flags\nmm/vmalloc.c:4342: * use __vmalloc() instead.\nmm/vmalloc.c-4343- *\n--\nmm/vmalloc.c=4606=static size_t aligned_vread_iter(struct iov_iter *iter,\n--\nmm/vmalloc.c-4623-\t\t * adding lock here means that we need to add overhead of\nmm/vmalloc.c:4624:\t\t * vmalloc()/vfree() calls for this _debug_ interface, rarely\nmm/vmalloc.c-4625-\t\t * used. Instead of that, we'll use an local mapping via\n--\nmm/vmalloc.c=4650=static size_t vmap_ram_vread_iter(struct iov_iter *iter, const char *addr,\n--\nmm/vmalloc.c-4749- * Note: In usual ops, vread_iter() is never necessary because the caller\nmm/vmalloc.c:4750: * should know vmalloc() area is valid and can use memcpy().\nmm/vmalloc.c-4751- * This is for routines which have to access vmalloc area without\n--\nmm/vmalloc.c=5058=struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,\n--\nmm/vmalloc.c-5199-\tfor (area = 0; area \u003c nr_vms; area++) {\nmm/vmalloc.c:5200:\t\tif (kasan_populate_vmalloc(vas[area]-\u003eva_start, sizes[area], gfp))\nmm/vmalloc.c-5201-\t\t\tgoto err_free_shadow;\n--\nmm/vmalloc.c-5218-\t * With hardware tag-based KASAN, marking is skipped for\nmm/vmalloc.c:5219:\t * non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().\nmm/vmalloc.c-5220-\t */\n--\nmm/vmalloc.c-5238-\t\tif (va)\nmm/vmalloc.c:5239:\t\t\tkasan_release_vmalloc(orig_start, orig_end,\nmm/vmalloc.c-5240-\t\t\t\tva-\u003eva_start, va-\u003eva_end,\n--\nmm/vmalloc.c-5289-\t\tif (va)\nmm/vmalloc.c:5290:\t\t\tkasan_release_vmalloc(orig_start, orig_end,\nmm/vmalloc.c-5291-\t\t\t\tva-\u003eva_start, va-\u003eva_end,\n"
} |
| 65/3 | 2026/10/28 02:00 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 18599 output: 35 thoughts: 36 Thoughts: Here's a summary of my thought process: **Diving into vmalloc Internals** Okay, so I need to understand how the kernel allocates virtual memory with `vmalloc`. Let's get right into it, I think the `__vmalloc_area_node` function in `mm/vmalloc.c` is probably where the core allocation logic resides. It's the standard implementation for non-contiguous allocations, and given my understanding of the system, that's where I need to start. Specifically, I'll focus around line 4034, as I recall that's roughly where the main allocation loop should be in the current kernel version. Time to dig in and see how the node selection and page assignment is handled. |
| 66/3 | 2026/10/28 02:01 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 4030,
"LineCount": 55
}Results: {
"Contents": "4030:\t\t\t\t\t__GFP_NORETRY | __GFP_RETRY_MAYFAIL |\\\n4031:\t\t\t\t\tGFP_NOFS | GFP_NOIO | GFP_KERNEL_ACCOUNT |\\\n4032:\t\t\t\t\tGFP_USER | __GFP_NOLOCKDEP | __GFP_SKIP_KASAN)\n4033:\t\n4034:\tstatic gfp_t vmalloc_fix_flags(gfp_t flags)\n4035:\t{\n4036:\t\tgfp_t invalid_mask = flags \u0026 ~GFP_VMALLOC_SUPPORTED;\n4037:\t\n4038:\t\tflags \u0026= GFP_VMALLOC_SUPPORTED;\n4039:\t\tWARN_ONCE(1, \"Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\\n\",\n4040:\t\t\t invalid_mask, \u0026invalid_mask, flags, \u0026flags);\n4041:\t\treturn flags;\n4042:\t}\n4043:\t\n4044:\t/**\n4045:\t * __vmalloc_node_range - allocate virtually contiguous memory\n4046:\t * @size:\t\t allocation size\n4047:\t * @align:\t\t desired alignment\n4048:\t * @start:\t\t vm area range start\n4049:\t * @end:\t\t vm area range end\n4050:\t * @gfp_mask:\t\t flags for the page level allocator\n4051:\t * @prot:\t\t protection mask for the allocated pages\n4052:\t * @vm_flags:\t\t additional vm area flags (e.g. %VM_NO_GUARD)\n4053:\t * @node:\t\t node to use for allocation or NUMA_NO_NODE\n4054:\t * @caller:\t\t caller's return address\n4055:\t *\n4056:\t * Allocate enough pages to cover @size from the page level\n4057:\t * allocator with @gfp_mask flags and map them into contiguous\n4058:\t * virtual range with protection @prot.\n4059:\t *\n4060:\t * Supported GFP classes: %GFP_KERNEL, %GFP_ATOMIC, %GFP_NOWAIT,\n4061:\t * %__GFP_RETRY_MAYFAIL, %__GFP_NORETRY, %GFP_NOFS and %GFP_NOIO.\n4062:\t * Zone modifiers are not supported.\n4063:\t * Please note %GFP_ATOMIC and %GFP_NOWAIT are supported only\n4064:\t * by __vmalloc().\n4065:\t *\n4066:\t * Retry modifiers: only %__GFP_NOFAIL is fully supported;\n4067:\t * %__GFP_NORETRY and %__GFP_RETRY_MAYFAIL are supported with limitation,\n4068:\t * i.e. page tables are allocated with NOWAIT semantic so they might fail\n4069:\t * under moderate memory pressure.\n4070:\t *\n4071:\t * %__GFP_NOWARN can be used to suppress failure messages.\n4072:\t *\n4073:\t * %__GFP_SKIP_KASAN can be used to skip unpoisoning of mapped pages\n4074:\t * (when prot=%PAGE_KERNEL).\n4075:\t *\n4076:\t * %VM_ALLOW_HUGE_VMAP allocates huge pages when possible and falls back to\n4077:\t * base pages if huge page allocation fails.\n4078:\t *\n4079:\t * %VM_REQUIRE_HUGE_VMAP implies %VM_ALLOW_HUGE_VMAP and fails instead of\n4080:\t * silently falling back to base pages.\n4081:\t *\n4082:\t * Can not be called from interrupt nor NMI contexts.\n4083:\t * Return: the address of the area or %NULL on failure\n4084:\t */\n"
} |
| 67/3 | 2026/10/28 02:01 | llm | kmsan-evaluator |
2mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 19834 output: 35 thoughts: 20 Thoughts: Okay, here's my interpretation of "Let's read further down in `__vmalloc_node_range_noprof`," tailored for an expert audience, as if it were my thought process: **Diving Deeper into `__vmalloc_node_range_noprof`** Alright, the initial overview is done. Now, let's drill down into `__vmalloc_node_range_noprof`. I need to understand the nuances of how this particular function is handling the virtual memory allocation, especially in the context it's being used. Specifically, I want to see the details of how the node-specific aspects are implemented. Is it employing direct manipulation of the page tables? What's the strategy for finding a suitable virtual address range? Are there any clever optimizations in place to minimize fragmentation or improve locality? I need to understand the interaction with the buddy allocator, or any other underlying memory management components. Any subtle details in this function could have significant performance implications. I'm looking for clues about the allocation strategy, potential locking issues (even in the "noprof" version, concurrency is always a consideration), and any potential error handling that might shed light on the system's robustness under memory pressure. Let's see what gems we can find in there! |
| 68/3 | 2026/10/28 02:03 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 4085,
"LineCount": 70
}Results: {
"Contents": "4085:\tvoid *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,\n4086:\t\t\t\tunsigned long start, unsigned long end, gfp_t gfp_mask,\n4087:\t\t\t\tpgprot_t prot, unsigned long vm_flags, int node,\n4088:\t\t\t\tconst void *caller)\n4089:\t{\n4090:\t\tstruct vm_struct *area;\n4091:\t\tvoid *ret;\n4092:\t\tkasan_vmalloc_flags_t kasan_flags = KASAN_VMALLOC_NONE;\n4093:\t\tunsigned long original_align = align;\n4094:\t\tunsigned int shift = PAGE_SHIFT;\n4095:\t\tbool skip_vmalloc_kasan = kasan_hw_tags_enabled() \u0026\u0026 (gfp_mask \u0026 __GFP_SKIP_KASAN);\n4096:\t\n4097:\t\tif (WARN_ON_ONCE(!size))\n4098:\t\t\treturn NULL;\n4099:\t\n4100:\t\tif ((size \u003e\u003e PAGE_SHIFT) \u003e totalram_pages()) {\n4101:\t\t\twarn_alloc(gfp_mask, NULL,\n4102:\t\t\t\t\"vmalloc error: size %lu, exceeds total pages\",\n4103:\t\t\t\tsize);\n4104:\t\t\treturn NULL;\n4105:\t\t}\n4106:\t\n4107:\t\t/* VM_REQUIRE_HUGE_VMAP implies VM_ALLOW_HUGE_VMAP */\n4108:\t\tif (vm_flags \u0026 VM_REQUIRE_HUGE_VMAP)\n4109:\t\t\tvm_flags |= VM_ALLOW_HUGE_VMAP;\n4110:\t\n4111:\t\tif (vmap_allow_huge \u0026\u0026 (vm_flags \u0026 VM_ALLOW_HUGE_VMAP)) {\n4112:\t\t\t/*\n4113:\t\t\t * Try huge pages. Only try for PAGE_KERNEL allocations,\n4114:\t\t\t * others like modules don't yet expect huge pages in\n4115:\t\t\t * their allocations due to apply_to_page_range not\n4116:\t\t\t * supporting them.\n4117:\t\t\t */\n4118:\t\n4119:\t\t\tif (arch_vmap_pmd_supported(prot) \u0026\u0026 size \u003e= PMD_SIZE)\n4120:\t\t\t\tshift = PMD_SHIFT;\n4121:\t\t\telse\n4122:\t\t\t\tshift = arch_vmap_pte_supported_shift(size);\n4123:\t\n4124:\t\t\talign = max(original_align, 1UL \u003c\u003c shift);\n4125:\t\t}\n4126:\t\n4127:\t\tif ((vm_flags \u0026 VM_REQUIRE_HUGE_VMAP) \u0026\u0026 shift == PAGE_SHIFT)\n4128:\t\t\treturn NULL;\n4129:\t\n4130:\tagain:\n4131:\t\tarea = __get_vm_area_node(size, align, shift, VM_ALLOC |\n4132:\t\t\t\t\t VM_UNINITIALIZED | vm_flags, start, end, node,\n4133:\t\t\t\t\t gfp_mask \u0026 ~__GFP_SKIP_KASAN, caller);\n4134:\t\tif (!area) {\n4135:\t\t\tbool nofail = gfp_mask \u0026 __GFP_NOFAIL;\n4136:\t\t\twarn_alloc(gfp_mask, NULL,\n4137:\t\t\t\t\"vmalloc error: size %lu, align 0x%lx, vm_struct allocation failed%s\",\n4138:\t\t\t\tsize, align, (nofail) ? \". Retrying.\" : \"\");\n4139:\t\t\tif (nofail) {\n4140:\t\t\t\tschedule_timeout_uninterruptible(1);\n4141:\t\t\t\tgoto again;\n4142:\t\t\t}\n4143:\t\t\tgoto fail;\n4144:\t\t}\n4145:\t\n4146:\t\t/*\n4147:\t\t * Prepare arguments for __vmalloc_area_node() and\n4148:\t\t * kasan_unpoison_vmalloc().\n4149:\t\t */\n4150:\t\tif (pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) {\n4151:\t\t\tif (kasan_hw_tags_enabled() \u0026\u0026 !skip_vmalloc_kasan) {\n4152:\t\t\t\t/*\n4153:\t\t\t\t * Modify protection bits to allow tagging.\n4154:\t\t\t\t * This must be done before mapping.\n"
} |
| 69/3 | 2026/10/28 02:03 | llm | kmsan-evaluator |
2mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 21309 output: 35 thoughts: 17 Thoughts: Okay, here's my interpretation of that request, formatted as requested: **Navigating Lines 4155-4200: A Focused Read** Alright, let's zero in on lines 4155 to 4200. My initial instinct, as always, is to assess the context. What's the overarching argument being made in the surrounding sections? Are there any key terms or concepts being developed that I should be particularly attuned to? I need to quickly establish the intellectual landscape surrounding these specific lines. This is crucial; I can't interpret these lines in isolation. They are building blocks in a more complex structure, and I need to understand the architecture. Once I have a grasp of the surrounding context, I'll then move to a more granular analysis. I'll read through those lines carefully, looking for specific rhetorical strategies, points of argumentation, any potential areas of ambiguity or weakness, etc. I'll be assessing the author's logic, considering possible counterarguments, and thinking about the implications of the points made. I will need to be methodical. This is where my expertise truly kicks in: I'll be immediately cataloging connections, comparing it to other texts I've read in this field, and perhaps even sketching out a preliminary critique based on what I encounter. This is almost automatic, as I try to read with the author's voice in my head. Ultimately, I'll strive to understand what the author is driving at and judge its place in the scholarly context. |
| 70/3 | 2026/10/28 02:06 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 4155,
"LineCount": 45
}Results: {
"Contents": "4155:\t\t\t\t */\n4156:\t\t\t\tprot = arch_vmap_pgprot_tagged(prot);\n4157:\t\n4158:\t\t\t\t/*\n4159:\t\t\t\t * Skip page_alloc poisoning and zeroing for physical\n4160:\t\t\t\t * pages backing VM_ALLOC mapping. Memory is instead\n4161:\t\t\t\t * poisoned and zeroed by kasan_unpoison_vmalloc().\n4162:\t\t\t\t */\n4163:\t\t\t\tgfp_mask |= __GFP_SKIP_KASAN | __GFP_SKIP_ZERO;\n4164:\t\t\t}\n4165:\t\n4166:\t\t\t/* Take note that the mapping is PAGE_KERNEL. */\n4167:\t\t\tkasan_flags |= KASAN_VMALLOC_PROT_NORMAL;\n4168:\t\t}\n4169:\t\n4170:\t\t/* Allocate physical pages and map them into vmalloc space. */\n4171:\t\tret = __vmalloc_area_node(area, gfp_mask, prot, shift, node);\n4172:\t\tif (!ret)\n4173:\t\t\tgoto fail;\n4174:\t\n4175:\t\t/*\n4176:\t\t * Mark the pages as accessible, now that they are mapped.\n4177:\t\t * The condition for setting KASAN_VMALLOC_INIT should complement the\n4178:\t\t * one in post_alloc_hook() with regards to the __GFP_SKIP_ZERO check\n4179:\t\t * to make sure that memory is initialized under the same conditions.\n4180:\t\t * Tag-based KASAN modes only assign tags to normal non-executable\n4181:\t\t * allocations, see __kasan_unpoison_vmalloc().\n4182:\t\t */\n4183:\t\tkasan_flags |= KASAN_VMALLOC_VM_ALLOC;\n4184:\t\tif (!want_init_on_free() \u0026\u0026 want_init_on_alloc(gfp_mask) \u0026\u0026\n4185:\t\t (gfp_mask \u0026 __GFP_SKIP_ZERO))\n4186:\t\t\tkasan_flags |= KASAN_VMALLOC_INIT;\n4187:\t\t/* KASAN_VMALLOC_PROT_NORMAL already set if required. */\n4188:\t\tif (!skip_vmalloc_kasan)\n4189:\t\t\tarea-\u003eaddr = kasan_unpoison_vmalloc(area-\u003eaddr, size, kasan_flags);\n4190:\t\n4191:\t\t/*\n4192:\t\t * In this function, newly allocated vm_struct has VM_UNINITIALIZED\n4193:\t\t * flag. It means that vm_struct is not fully initialized.\n4194:\t\t * Now, it is fully initialized, so remove this flag here.\n4195:\t\t */\n4196:\t\tclear_vm_uninitialized_flag(area);\n4197:\t\n4198:\t\tif (!(vm_flags \u0026 VM_DEFER_KMEMLEAK))\n4199:\t\t\tkmemleak_vmalloc(area, PAGE_ALIGN(size), gfp_mask);\n"
} |
| 71/3 | 2026/10/28 02:06 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 22465 output: 34 thoughts: 38 Thoughts: Okay, let's see. My mind's immediately drawn to this `__vmalloc_area_node` function. I need to understand what's happening at the allocation level, especially within the context of vmalloc. The core of my interest is... **Deciphering `__vmalloc_area_node` and its GFP flags**. Specifically, I need to know what `gfp` flags it's using when it's allocating pages. Understanding those flags gives me key insights into the constraints and characteristics of the memory being allocated via `vmalloc`. Let's dive in and dissect that function to get the details I need. |
| 72/3 | 2026/10/28 02:08 | tool | grepper |
0mArgs:{
"Expression": "__vmalloc_area_node",
"PathPrefixes": [
"mm/vmalloc.c"
]
}Results: {
"Output": "mm/vmalloc.c=3854=static void cleanup_vm_area_work(struct work_struct *work)\n--\nmm/vmalloc.c-3871-/*\nmm/vmalloc.c:3872: * Helper for __vmalloc_area_node() to defer cleanup\nmm/vmalloc.c-3873- * of partially initialized vm_struct in error paths.\n--\nmm/vmalloc.c=3915=memalloc_restore_scope(unsigned int flags)\n--\nmm/vmalloc.c-3920-\nmm/vmalloc.c:3921:static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,\nmm/vmalloc.c-3922-\t\t\t\t pgprot_t prot, unsigned int page_shift,\n--\nmm/vmalloc.c=4085=void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,\n--\nmm/vmalloc.c-4146-\t/*\nmm/vmalloc.c:4147:\t * Prepare arguments for __vmalloc_area_node() and\nmm/vmalloc.c-4148-\t * kasan_unpoison_vmalloc().\n--\nmm/vmalloc.c-4170-\t/* Allocate physical pages and map them into vmalloc space. */\nmm/vmalloc.c:4171:\tret = __vmalloc_area_node(area, gfp_mask, prot, shift, node);\nmm/vmalloc.c-4172-\tif (!ret)\n"
} |
| 73/3 | 2026/10/28 02:08 | llm | kmsan-evaluator |
2mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 23076 output: 35 thoughts: 13 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving into `__vmalloc_area_node`** Alright, let's get into the details of `__vmalloc_area_node`. I need to brush up on this again; it's fundamental to understanding dynamic memory allocation within the kernel, particularly for larger contiguous chunks. I'm focusing on this node specifically because it's the core of how `vmalloc` manages non-contiguous physical pages. I want to see how this function is implemented and if it's got any clever memory management tricks that I can steal for my own code. Also, I need to check how it deals with fragmentation and how it does the best-fit search of the free pages. I want to understand the data structures it manipulates: the area descriptor itself, the associated page lists, and how they're interconnected. I'm thinking about the implications of the NUMA awareness here too. How does `__vmalloc_area_node` handle different node memory configurations? I'll probably look for locks and synchronization mechanisms. I need to refresh my knowledge of the memory barrier implementations. I'm specifically interested in the interactions with the page allocator (`__alloc_pages_node` etc.), the virtual memory mapping functions (`vm_map_ram` etc.), and the error handling. Let's see how resilient this function is. Any edge cases it handles? I need to be sure that my understanding of the vmalloc implementation is up to date, to spot possible performance bottlenecks and memory leaks. |
| 74/3 | 2026/10/28 02:11 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 3920,
"LineCount": 40
}Results: {
"Contents": "3920:\t\n3921:\tstatic void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,\n3922:\t\t\t\t\t pgprot_t prot, unsigned int page_shift,\n3923:\t\t\t\t\t int node)\n3924:\t{\n3925:\t\tconst gfp_t nested_gfp = (gfp_mask \u0026 GFP_RECLAIM_MASK) | __GFP_ZERO;\n3926:\t\tbool nofail = gfp_mask \u0026 __GFP_NOFAIL;\n3927:\t\tunsigned long addr = (unsigned long)area-\u003eaddr;\n3928:\t\tunsigned long size = get_vm_area_size(area);\n3929:\t\tunsigned long array_size;\n3930:\t\tunsigned long nr_small_pages = size \u003e\u003e PAGE_SHIFT;\n3931:\t\tunsigned int page_order = page_shift - PAGE_SHIFT;\n3932:\t\tunsigned int flags;\n3933:\t\tint ret;\n3934:\t\n3935:\t\tarray_size = nr_small_pages * sizeof(struct page *);\n3936:\t\n3937:\t\t/* __GFP_NOFAIL and \"noblock\" flags are mutually exclusive. */\n3938:\t\tif (!gfpflags_allow_blocking(gfp_mask))\n3939:\t\t\tnofail = false;\n3940:\t\n3941:\t\tif (!(gfp_mask \u0026 (GFP_DMA | GFP_DMA32)))\n3942:\t\t\tgfp_mask |= __GFP_HIGHMEM;\n3943:\t\n3944:\t\t/* Please note that the recursion is strictly bounded. */\n3945:\t\tif (array_size \u003e PAGE_SIZE) {\n3946:\t\t\tarea-\u003epages = __vmalloc_node_noprof(array_size, 1, nested_gfp, node,\n3947:\t\t\t\t\t\tarea-\u003ecaller);\n3948:\t\t} else {\n3949:\t\t\tarea-\u003epages = kmalloc_node_noprof(array_size, nested_gfp, node);\n3950:\t\t}\n3951:\t\n3952:\t\tif (!area-\u003epages) {\n3953:\t\t\twarn_alloc(gfp_mask, NULL,\n3954:\t\t\t\t\"vmalloc error: size %lu, failed to allocated page array size %lu\",\n3955:\t\t\t\tnr_small_pages * PAGE_SIZE, array_size);\n3956:\t\t\tgoto fail;\n3957:\t\t}\n3958:\t\n3959:\t\t/*\n"
} |
| 75/3 | 2026/10/28 02:11 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 24120 output: 35 thoughts: 15 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: **Diving into `__vmalloc_area_node`** Alright, so the instruction says "Let's read further in `__vmalloc_area_node`". My immediate thought is, *Why?* What's the context? Are we debugging a `vmalloc` issue? Trying to understand the allocation algorithm? Perhaps looking for a performance bottleneck? Or maybe just brushing up on the kernel's memory management internals. Whatever the reason, `__vmalloc_area_node` is the jumping-off point for a deep dive. I'm mentally parsing this function's purpose: it likely deals with the core logic for allocating virtually contiguous memory within the kernel's address space. It's the engine that drives `vmalloc`, which means it touches on the complexities of page table manipulation, physical memory mapping, and potentially dealing with fragmentation. I need to keep in mind that this function is part of a complex system. Any modification or observation might have unintended and far-reaching effects on the system. I also need to understand how this is connected to the other `vmalloc` functions. It's imperative that I understand the relationships between the functions involved, to ensure that I have the complete picture. The next step will depend on what I find there. |
| 76/3 | 2026/10/28 02:11 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 3960,
"LineCount": 40
}Results: {
"Contents": "3960:\t\t * High-order nofail allocations are really expensive and\n3961:\t\t * potentially dangerous (pre-mature OOM, disruptive reclaim\n3962:\t\t * and compaction etc.\n3963:\t\t *\n3964:\t\t * Please note, the __vmalloc_node_range_noprof() falls-back\n3965:\t\t * to order-0 pages if high-order attempt is unsuccessful.\n3966:\t\t */\n3967:\t\tarea-\u003enr_pages = vm_area_alloc_pages(\n3968:\t\t\t\tvmalloc_gfp_adjust(gfp_mask, page_order), node,\n3969:\t\t\t\tpage_order, nr_small_pages, area-\u003epages);\n3970:\t\n3971:\t\t/*\n3972:\t\t * If not enough pages were obtained to accomplish an\n3973:\t\t * allocation request, free them via vfree() if any.\n3974:\t\t */\n3975:\t\tif (area-\u003enr_pages != nr_small_pages) {\n3976:\t\t\t/*\n3977:\t\t\t * vm_area_alloc_pages() can fail due to insufficient memory but\n3978:\t\t\t * also:-\n3979:\t\t\t *\n3980:\t\t\t * - a pending fatal signal\n3981:\t\t\t * - insufficient huge page-order pages\n3982:\t\t\t *\n3983:\t\t\t * Since we always retry allocations at order-0 in the huge page\n3984:\t\t\t * case a warning for either is spurious.\n3985:\t\t\t */\n3986:\t\t\tif (!fatal_signal_pending(current) \u0026\u0026 page_order == 0)\n3987:\t\t\t\twarn_alloc(gfp_mask, NULL,\n3988:\t\t\t\t\t\"vmalloc error: size %lu, failed to allocate pages\",\n3989:\t\t\t\t\tnr_small_pages * PAGE_SIZE);\n3990:\t\t\tgoto fail;\n3991:\t\t}\n3992:\t\n3993:\t\t/*\n3994:\t\t * page tables allocations ignore external gfp mask, enforce it\n3995:\t\t * by the scope API\n3996:\t\t */\n3997:\t\tflags = memalloc_apply_gfp_scope(gfp_mask);\n3998:\t\tdo {\n3999:\t\t\tret = __vmap_pages_range(addr, addr + size, prot, area-\u003epages,\n"
} |
| 77/3 | 2026/10/28 02:11 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 25081 output: 34 thoughts: 23 Thoughts: Here's a first-person summary, tailored for an expert audience, based on your prompt: **Diving into Memory Allocation** Okay, time to get my hands dirty. I'm going to start by taking a close look at `vm_area_alloc_pages` and how it interacts with `vmalloc_gfp_adjust`. I need to refresh my understanding of their interplay, especially considering potential memory fragmentation issues, and how these functions handle the granularity of allocation under various GFP flags. Specifically, I'm interested in how `vmalloc_gfp_adjust` might be influencing the page allocation strategy within `vm_area_alloc_pages`, and if there are any opportunities to fine-tune that interaction for performance or to minimize contention. I need to keep in mind possible lock-related issues and how to minimize them, especially in highly parallel environments. This is a crucial area to revisit when I consider the efficiency and robustness of the virtual memory subsystem. |
| 78/3 | 2026/10/28 02:13 | tool | grepper |
0mArgs:{
"Expression": "vmalloc_gfp_adjust",
"PathPrefixes": [
"mm/vmalloc.c"
]
}Results: {
"Output": "mm/vmalloc.c=3709=EXPORT_SYMBOL_GPL(vmap_pfn);\n--\nmm/vmalloc.c-3714- */\nmm/vmalloc.c:3715:static inline gfp_t vmalloc_gfp_adjust(gfp_t flags, const bool large)\nmm/vmalloc.c-3716-{\n--\nmm/vmalloc.c=3724=vm_area_alloc_pages(gfp_t gfp, int nid,\n--\nmm/vmalloc.c-3732-\tunsigned int large_order = ilog2(nr_remaining);\nmm/vmalloc.c:3733:\tgfp_t large_gfp = vmalloc_gfp_adjust(gfp, large_order) \u0026 ~__GFP_DIRECT_RECLAIM;\nmm/vmalloc.c-3734-\n--\nmm/vmalloc.c=3921=static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,\n--\nmm/vmalloc.c-3967-\tarea-\u003enr_pages = vm_area_alloc_pages(\nmm/vmalloc.c:3968:\t\t\tvmalloc_gfp_adjust(gfp_mask, page_order), node,\nmm/vmalloc.c-3969-\t\t\tpage_order, nr_small_pages, area-\u003epages);\n"
} |
| 79/3 | 2026/10/28 02:13 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 25700 output: 35 thoughts: 21 Thoughts: Okay, here's my interpretation of what's going on, thinking through this code: **Analyzing `vmalloc_gfp_adjust` in the Kernel** Alright, let's dive into this `vmalloc_gfp_adjust` function. I see it starts at line 3714. This is a crucial function; it hints at how the kernel is handling allocation flags within the virtual memory management (vmalloc) subsystem. Given the name, I'm guessing it's about tweaking the `gfp_mask`, which controls memory allocation behavior. I need to understand what this adjustment involves and why it's necessary. Is this about adding flags, removing them, checking for something? Is this related to memory zones? I'll need to see how the flags are passed to the `vmalloc` system for allocation. Let's see how this affects the allocation and, potentially, the performance. This is the critical step in understanding the virtual memory management. |
| 80/3 | 2026/10/28 02:14 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 3714,
"LineCount": 25
}Results: {
"Contents": "3714:\t */\n3715:\tstatic inline gfp_t vmalloc_gfp_adjust(gfp_t flags, const bool large)\n3716:\t{\n3717:\t\tflags |= __GFP_NOWARN;\n3718:\t\tif (large)\n3719:\t\t\tflags \u0026= ~__GFP_NOFAIL;\n3720:\t\treturn flags;\n3721:\t}\n3722:\t\n3723:\tstatic inline unsigned long\n3724:\tvm_area_alloc_pages(gfp_t gfp, int nid,\n3725:\t\t\tunsigned int order, unsigned long nr_pages, struct page **pages)\n3726:\t{\n3727:\t\tunsigned long nr_allocated = 0;\n3728:\t\tunsigned long nr_remaining = nr_pages;\n3729:\t\tunsigned int max_attempt_order = MAX_PAGE_ORDER;\n3730:\t\tstruct page *page;\n3731:\t\tint i;\n3732:\t\tunsigned int large_order = ilog2(nr_remaining);\n3733:\t\tgfp_t large_gfp = vmalloc_gfp_adjust(gfp, large_order) \u0026 ~__GFP_DIRECT_RECLAIM;\n3734:\t\n3735:\t\tlarge_order = min(max_attempt_order, large_order);\n3736:\t\n3737:\t\t/*\n3738:\t\t * Initially, attempt to have the page allocator give us large order\n"
} |
| 81/3 | 2026/10/28 02:14 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 26357 output: 36 thoughts: 23 Thoughts: Okay, here's the summary, tailored for an expert audience, in the first person, reflecting the thought process: **Memory Allocation Question** Wait a minute, I need to be sure about something with `__vmalloc`. Does it actually zero the memory it allocates, or is that something I need to handle separately? I know there can be differences between the behavior of these functions. Let's not assume anything here. To be absolutely certain, I need to go straight to the source. Time to dig into the definition of `__vmalloc` itself. Gotta confirm the memory initialization behavior explicitly! |
| 82/3 | 2026/10/28 02:14 | tool | grepper |
0mArgs:{
"Expression": "__vmalloc_node_noprof",
"PathPrefixes": [
"mm/vmalloc.c"
]
}Results: {
"Output": "mm/vmalloc.c=3921=static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,\n--\nmm/vmalloc.c-3945-\tif (array_size \u003e PAGE_SIZE) {\nmm/vmalloc.c:3946:\t\tarea-\u003epages = __vmalloc_node_noprof(array_size, 1, nested_gfp, node,\nmm/vmalloc.c-3947-\t\t\t\t\tarea-\u003ecaller);\n--\nmm/vmalloc.c=4085=void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,\n--\nmm/vmalloc.c-4228- */\nmm/vmalloc.c:4229:void *__vmalloc_node_noprof(unsigned long size, unsigned long align,\nmm/vmalloc.c-4230-\t\t\t gfp_t gfp_mask, int node, const void *caller)\n--\nmm/vmalloc.c-4240-#ifdef CONFIG_TEST_VMALLOC_MODULE\nmm/vmalloc.c:4241:EXPORT_SYMBOL_GPL(__vmalloc_node_noprof);\nmm/vmalloc.c-4242-#endif\n--\nmm/vmalloc.c=4244=void *__vmalloc_noprof(unsigned long size, gfp_t gfp_mask)\n--\nmm/vmalloc.c-4247-\t\tgfp_mask = vmalloc_fix_flags(gfp_mask);\nmm/vmalloc.c:4248:\treturn __vmalloc_node_noprof(size, 1, gfp_mask, NUMA_NO_NODE,\nmm/vmalloc.c-4249-\t\t\t\t__builtin_return_address(0));\n--\nmm/vmalloc.c=4265=void *vmalloc_noprof(unsigned long size)\nmm/vmalloc.c-4266-{\nmm/vmalloc.c:4267:\treturn __vmalloc_node_noprof(size, 1, GFP_KERNEL, NUMA_NO_NODE,\nmm/vmalloc.c-4268-\t\t\t\t__builtin_return_address(0));\n--\nmm/vmalloc.c=4308=void *vzalloc_noprof(unsigned long size)\nmm/vmalloc.c-4309-{\nmm/vmalloc.c:4310:\treturn __vmalloc_node_noprof(size, 1, GFP_KERNEL | __GFP_ZERO, NUMA_NO_NODE,\nmm/vmalloc.c-4311-\t\t\t\t__builtin_return_address(0));\n--\nmm/vmalloc.c=4346=void *vmalloc_node_noprof(unsigned long size, int node)\nmm/vmalloc.c-4347-{\nmm/vmalloc.c:4348:\treturn __vmalloc_node_noprof(size, 1, GFP_KERNEL, node,\nmm/vmalloc.c-4349-\t\t\t__builtin_return_address(0));\n--\nmm/vmalloc.c=4364=void *vzalloc_node_noprof(unsigned long size, int node)\nmm/vmalloc.c-4365-{\nmm/vmalloc.c:4366:\treturn __vmalloc_node_noprof(size, 1, GFP_KERNEL | __GFP_ZERO, node,\nmm/vmalloc.c-4367-\t\t\t\t__builtin_return_address(0));\n--\nmm/vmalloc.c=4404=void *vrealloc_node_align_noprof(const void *p, size_t size, unsigned long align,\n--\nmm/vmalloc.c-4516-\t/* TODO: Grow the vm_area, i.e. allocate and map additional pages. */\nmm/vmalloc.c:4517:\tn = __vmalloc_node_noprof(size, align, flags, nid, __builtin_return_address(0));\nmm/vmalloc.c-4518-\n--\nmm/vmalloc.c=4552=void *vmalloc_32_noprof(unsigned long size)\nmm/vmalloc.c-4553-{\nmm/vmalloc.c:4554:\treturn __vmalloc_node_noprof(size, 1, GFP_VMALLOC32, NUMA_NO_NODE,\nmm/vmalloc.c-4555-\t\t\t__builtin_return_address(0));\n"
} |
| 83/3 | 2026/10/28 02:14 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 27676 output: 19 thoughts: 89 Thoughts: Okay, here's my understanding, tailored for an expert audience, as if it were my own thought process: **VMalloc Allocation Behavior and KMSAN Interaction** Right, so, a quick sanity check on `vmalloc()` versus the zero-filled variants. I need to be absolutely sure about the memory initialization behavior. `vmalloc()` *specifically* does NOT pass `__GFP_ZERO`. Okay, got that. So if you want zero-initialized memory in a vmalloc region, you're looking at `vzalloc()` or `vcalloc()` because those *do* specify `__GFP_ZERO`. And a side note: `vmalloc_array` just uses `GFP_KERNEL` without `__GFP_ZERO` meaning it is not zeroed. Now, a critical question arises: how does KMSAN handle these vmalloc allocations? Does KMSAN track them appropriately? I need to dig into how KMSAN interacts with these different allocation patterns because that's where the potential instrumentation nuances really come into play. Let's get that verified. |
| 84/3 | 2026/10/28 02:14 | tool | grepper |
0mArgs:{
"Expression": "kmsan.*vmalloc"
}Results: {
"Output": "mm/kmsan/core.c=192=void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b,\n--\nmm/kmsan/core.c-239-\nmm/kmsan/core.c:240:struct page *kmsan_vmalloc_to_page_or_null(void *vaddr)\nmm/kmsan/core.c-241-{\n--\nmm/kmsan/hooks.c=149=static void kmsan_iounmap_pages(unsigned long start, unsigned long end)\n--\nmm/kmsan/hooks.c-163-\t i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {\nmm/kmsan/hooks.c:164:\t\tshadow = kmsan_vmalloc_to_page_or_null((void *)v_shadow);\nmm/kmsan/hooks.c:165:\t\torigin = kmsan_vmalloc_to_page_or_null((void *)v_origin);\nmm/kmsan/hooks.c-166-\t\tif (shadow)\n--\nmm/kmsan/kmsan.h=165=void kmsan_internal_check_memory(void *addr, size_t size,\n--\nmm/kmsan/kmsan.h-167-\nmm/kmsan/kmsan.h:168:struct page *kmsan_vmalloc_to_page_or_null(void *vaddr);\nmm/kmsan/kmsan.h-169-void kmsan_setup_meta(struct page *page, struct page *shadow,\n--\nmm/kmsan/kmsan.h-172-/*\nmm/kmsan/kmsan.h:173: * kmsan_internal_is_module_addr() and kmsan_internal_is_vmalloc_addr() are\nmm/kmsan/kmsan.h-174- * non-instrumented versions of is_module_address() and is_vmalloc_addr() that\n--\nmm/kmsan/kmsan.h=177=static inline bool kmsan_internal_is_module_addr(void *vaddr)\n--\nmm/kmsan/kmsan.h-181-\nmm/kmsan/kmsan.h:182:static inline bool kmsan_internal_is_vmalloc_addr(void *addr)\nmm/kmsan/kmsan.h-183-{\n--\nmm/kmsan/shadow.c=56=static unsigned long vmalloc_meta(void *addr, bool is_origin)\n--\nmm/kmsan/shadow.c-60-\tKMSAN_WARN_ON(is_origin \u0026\u0026 !IS_ALIGNED(addr64, KMSAN_ORIGIN_SIZE));\nmm/kmsan/shadow.c:61:\tif (kmsan_internal_is_vmalloc_addr(addr)) {\nmm/kmsan/shadow.c-62-\t\toff = addr64 - VMALLOC_START;\n--\nmm/kmsan/shadow.c=125=void *kmsan_get_metadata(void *address, bool is_origin)\n--\nmm/kmsan/shadow.c-133-\taddress = (void *)addr;\nmm/kmsan/shadow.c:134:\tif (kmsan_internal_is_vmalloc_addr(address) ||\nmm/kmsan/shadow.c-135-\t kmsan_internal_is_module_addr(address))\n"
} |
| 85/3 | 2026/10/28 02:14 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 28861 output: 24 thoughts: 432 Thoughts: **Analyzing `memfd_luo.c` for Memory Management**
Okay, let's dive into `memfd_luo.c`. First, I need to understand the change. What was the original allocation logic? Ah, right, it was using `vcalloc`:
```c
- folios_ser = vcalloc(nr_folios, sizeof(*folios_ser));
- if (!folios_ser) {
- err = -ENOMEM;
- goto err_unpin;
- }
```
Now, it's using a combination of `vmalloc_array` with dynamic resizing using `vrealloc`:
```c
+ end = DIV_ROUND_UP_ULL(size, PAGE_SIZE);
+ max_folios = end;
+ folios_ser = vmalloc_array(max_folios, sizeof(*folios_ser));
+ if (!folios_ser)
+ return -ENOMEM;
```
Interesting, so it pre-allocates based on the *maximum* size, then potentially shrinks it later using `vrealloc`. I see the `nr_folios` counter increasing.
```c
+ err = memfd_luo_preserve_folio(folio, &folios_ser[nr_folios]);
+ index = folio_next_index(folio);
...
+ nr_folios++;
```
The key here is the "Free the unused tail" comment.
```c
+ /*
+ * Free the unused tail so it doesn't get preserved. If vrealloc fails,
+ * the folios_ser is still valid.
+ */
+ shrunk = vrealloc(folios_ser, array_size(nr_folios, sizeof(*folios_ser)),
+ GFP_KERNEL);
+ if (shrunk)
+ folios_ser = shrunk;
+
+ err = kho_preserve_vmalloc(folios_ser, kho_vmalloc);
```
This is smart. Avoids allocating more memory than necessary by shrinking it down after determining the actual number of folios. And then it calls `kho_preserve_vmalloc`, which I need to investigate, but before that, I need to know about `struct memfd_luo_folio_ser`! Let's get more context on that structure.
|
| 86/3 | 2026/10/28 02:15 | tool | grepper |
0mArgs:{
"Expression": "struct memfd_luo_folio_ser"
}Results: {
"Output": "include/linux/kho/abi/memfd.h-47-/**\ninclude/linux/kho/abi/memfd.h:48: * struct memfd_luo_folio_ser - Serialized state of a single folio.\ninclude/linux/kho/abi/memfd.h-49- * @pfn: The page frame number of the folio.\n--\ninclude/linux/kho/abi/memfd.h-52- */\ninclude/linux/kho/abi/memfd.h:53:struct memfd_luo_folio_ser {\ninclude/linux/kho/abi/memfd.h-54-\tu64 pfn:52;\n--\ninclude/linux/kho/abi/memfd.h-78- * @folios: KHO vmalloc descriptor pointing to the array of\ninclude/linux/kho/abi/memfd.h:79: * struct memfd_luo_folio_ser.\ninclude/linux/kho/abi/memfd.h-80- */\n--\nmm/memfd_luo.c-91-\nmm/memfd_luo.c:92:static void memfd_luo_put_folios(const struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-93-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-97-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:98:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-99-\t\tstruct folio *folio;\n--\nmm/memfd_luo.c=152=static int memfd_luo_preserve_folio(struct folio *folio,\nmm/memfd_luo.c:153:\t\t\t\t struct memfd_luo_folio_ser *pfolio)\nmm/memfd_luo.c-154-{\n--\nmm/memfd_luo.c=189=static int memfd_luo_preserve_folios(struct file *file,\nmm/memfd_luo.c-190-\t\t\t\t struct kho_vmalloc *kho_vmalloc,\nmm/memfd_luo.c:191:\t\t\t\t struct memfd_luo_folio_ser **out_folios_ser,\nmm/memfd_luo.c-192-\t\t\t\t u64 *nr_foliosp)\nmm/memfd_luo.c-193-{\nmm/memfd_luo.c:194:\tstruct memfd_luo_folio_ser *folios_ser, *shrunk;\nmm/memfd_luo.c-195-\tstruct inode *inode = file_inode(file);\n--\nmm/memfd_luo.c=306=static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,\nmm/memfd_luo.c:307:\t\t\t\t\tstruct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-308-\t\t\t\t\tu64 nr_folios)\n--\nmm/memfd_luo.c=318=static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\n--\nmm/memfd_luo.c-320-\tstruct inode *inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:321:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c-322-\tstruct memfd_luo_ser *ser;\n--\nmm/memfd_luo.c=397=static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)\n--\nmm/memfd_luo.c-416-\nmm/memfd_luo.c:417:static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-418-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-422-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:423:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-424-\t\tstruct folio *folio;\n--\nmm/memfd_luo.c=442=static void memfd_luo_finish(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-443-{\nmm/memfd_luo.c:444:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c-445-\tstruct memfd_luo_ser *ser;\n--\nmm/memfd_luo.c=472=static int memfd_luo_retrieve_folios(struct file *file,\nmm/memfd_luo.c:473:\t\t\t\t struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-474-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-483-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:484:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-485-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-555-\tfor (long j = i + 1; j \u003c nr_folios; j++) {\nmm/memfd_luo.c:556:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[j];\nmm/memfd_luo.c-557-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c=573=static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-574-{\nmm/memfd_luo.c:575:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c-576-\tstruct memfd_luo_ser *ser;\n"
} |
| 87/3 | 2026/10/28 02:15 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 31487 output: 39 thoughts: 39 Thoughts: Here's my summary, as if I were thinking it: **Diving into `memfd_luo_folio_ser` Definition** Alright, time to dig into the kernel's `memfd` implementation. I need to refresh my memory on how serialized folio data is handled within the `memfd` mechanism. The logical place to start is the header file, specifically, `include/linux/kho/abi/memfd.h`. Let's grab that file and check out the definition of `struct memfd_luo_folio_ser`. I'm interested in the structure itself, and its specific members, as it tells the story of how data is represented on disk and in memory during these operations. I suspect I might find insights related to data layout, versioning, or other details relevant to the serialization process. This should give me the foundation for the next stage of investigation. |
| 88/3 | 2026/10/28 02:15 | tool | read-file |
0mArgs:{
"File": "include/linux/kho/abi/memfd.h",
"FirstLine": 40,
"LineCount": 45
}Results: {
"Contents": " 40:\t * MEMFD_LUO_FOLIO_UPTODATE - The folio is up-to-date.\n 41:\t *\n 42:\t * An up-to-date folio has been zeroed out. shmem zeroes out folios on first\n 43:\t * use. This flag tracks which folios need zeroing.\n 44:\t */\n 45:\t#define MEMFD_LUO_FOLIO_UPTODATE\tBIT(1)\n 46:\t\n 47:\t/**\n 48:\t * struct memfd_luo_folio_ser - Serialized state of a single folio.\n 49:\t * @pfn: The page frame number of the folio.\n 50:\t * @flags: Flags to describe the state of the folio.\n 51:\t * @index: The page offset (pgoff_t) of the folio within the original file.\n 52:\t */\n 53:\tstruct memfd_luo_folio_ser {\n 54:\t\tu64 pfn:52;\n 55:\t\tu64 flags:12;\n 56:\t\tu64 index;\n 57:\t} __packed;\n 58:\t\n 59:\t/*\n 60:\t * The set of seals this version supports preserving. If support for any new\n 61:\t * seals is needed, add it here and bump version.\n 62:\t */\n 63:\t#define MEMFD_LUO_ALL_SEALS (F_SEAL_SEAL | \\\n 64:\t\t\t\t F_SEAL_SHRINK | \\\n 65:\t\t\t\t F_SEAL_GROW | \\\n 66:\t\t\t\t F_SEAL_WRITE | \\\n 67:\t\t\t\t F_SEAL_FUTURE_WRITE | \\\n 68:\t\t\t\t F_SEAL_EXEC)\n 69:\t\n 70:\t/**\n 71:\t * struct memfd_luo_ser - Main serialization structure for a memfd.\n 72:\t * @pos: The file's current position (f_pos).\n 73:\t * @size: The total size of the file in bytes (i_size).\n 74:\t * @seals: The seals present on the memfd. The seals are uABI so it is safe\n 75:\t * to directly use them in the ABI.\n 76:\t * @flags: Flags for the file. Unused flag bits must be set to 0.\n 77:\t * @nr_folios: Number of folios in the folios array.\n 78:\t * @folios: KHO vmalloc descriptor pointing to the array of\n 79:\t * struct memfd_luo_folio_ser.\n 80:\t */\n 81:\tstruct memfd_luo_ser {\n 82:\t\tu64 pos;\n 83:\t\tu64 size;\n 84:\t\tu32 seals;\n"
} |
| 89/3 | 2026/10/28 02:15 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 32501 output: 20 thoughts: 372 Thoughts: **Analyzing the Serialization Structure and Potential Issues**
Okay, let's break this down. I'm looking at `struct memfd_luo_folio_ser`:
```c
struct memfd_luo_folio_ser {
u64 pfn:52;
u64 flags:12;
u64 index;
} __packed;
```
Right, so this is a 16-byte structure: an 8-byte bitfield (`pfn` and `flags`) followed by another 8-byte `index`, no padding, as expected with `__packed`. Then, in `memfd_luo_preserve_folio`, it seems straightforward. `pfn` gets the folio's page frame number, `flags` are set (specifically, `MEMFD_LUO_FOLIO_DIRTY` and `MEMFD_LUO_FOLIO_UPTODATE`), and `index` takes the folio's index. All fields are being written; no obvious problems there.
But then, I see this `vrealloc` call:
```c
shrunk = vrealloc(folios_ser, array_size(nr_folios, sizeof(*folios_ser)), GFP_KERNEL);
if (shrunk)
folios_ser = shrunk;
```
Ah, that's where things get interesting, and potentially problematic. What if `vrealloc` fails? The code *doesn't* check `shrunk` before attempting to use the newly allocated memory. If `vrealloc` fails, `folios_ser` will still point to the original, potentially smaller, allocation, and we are then trying to access memory that doesn't exist, which can lead to issues.
And the next thing I'm asking is: How many elements are actually initialized? We are only initializing up to `nr_folios`, which is the correct number of elements given the size calculation. The problem here is that the memory may not be properly de-allocated and is then used by a subsequent call.
And it leads me to the function call: `kho_preserve_vmalloc(folios_ser, kho_vmalloc);`. I need to check what this function does because there may be an underlying issue within.
|
| 90/3 | 2026/10/28 02:16 | tool | grepper |
0mArgs:{
"Expression": "kho_preserve_vmalloc"
}Results: {
"Output": "include/linux/kexec_handover.h=23=void kho_unpreserve_pages(struct page *page, unsigned long nr_pages);\ninclude/linux/kexec_handover.h:24:int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation);\ninclude/linux/kexec_handover.h-25-void kho_unpreserve_vmalloc(struct kho_vmalloc *preservation);\n--\ninclude/linux/kexec_handover.h=74=static inline void kho_unpreserve_pages(struct page *page, unsigned int nr_pages) { }\ninclude/linux/kexec_handover.h-75-\ninclude/linux/kexec_handover.h:76:static inline int kho_preserve_vmalloc(void *ptr,\ninclude/linux/kexec_handover.h-77-\t\t\t\t struct kho_vmalloc *preservation)\n--\nkernel/liveupdate/kexec_handover.c=1329=static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk,\n--\nkernel/liveupdate/kexec_handover.c-1343-/**\nkernel/liveupdate/kexec_handover.c:1344: * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec\nkernel/liveupdate/kexec_handover.c-1345- * @ptr: pointer to the area in vmalloc address space\n--\nkernel/liveupdate/kexec_handover.c-1357- */\nkernel/liveupdate/kexec_handover.c:1358:int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)\nkernel/liveupdate/kexec_handover.c-1359-{\n--\nkernel/liveupdate/kexec_handover.c-1408-}\nkernel/liveupdate/kexec_handover.c:1409:EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);\nkernel/liveupdate/kexec_handover.c-1410-\n--\nkernel/liveupdate/kexec_handover.c-1412- * kho_unpreserve_vmalloc - unpreserve memory allocated with vmalloc()\nkernel/liveupdate/kexec_handover.c:1413: * @preservation: preservation metadata returned by kho_preserve_vmalloc()\nkernel/liveupdate/kexec_handover.c-1414- *\nkernel/liveupdate/kexec_handover.c-1415- * Instructs KHO to unpreserve the area in vmalloc address space that was\nkernel/liveupdate/kexec_handover.c:1416: * previously preserved with kho_preserve_vmalloc().\nkernel/liveupdate/kexec_handover.c-1417- */\n--\nkernel/liveupdate/kexec_handover.c=1431=EXPORT_SYMBOL_GPL(kho_unpreserve_vmalloc);\n--\nkernel/liveupdate/kexec_handover.c-1438- * Recreates an area in vmalloc address space and populates it with memory that\nkernel/liveupdate/kexec_handover.c:1439: * was preserved using kho_preserve_vmalloc().\nkernel/liveupdate/kexec_handover.c-1440- *\n--\nlib/test_kho.c=54=static int kho_test_preserve_data(struct kho_test_state *state)\n--\nlib/test_kho.c-63-\nlib/test_kho.c:64:\terr = kho_preserve_vmalloc(folios_info, \u0026folios_info_phys);\nlib/test_kho.c-65-\tif (err)\n--\nmm/memfd_luo.c=189=static int memfd_luo_preserve_folios(struct file *file,\n--\nmm/memfd_luo.c-283-\nmm/memfd_luo.c:284:\terr = kho_preserve_vmalloc(folios_ser, kho_vmalloc);\nmm/memfd_luo.c-285-\tif (err)\n"
} |
| 91/3 | 2026/10/28 02:16 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 34402 output: 28 thoughts: 905 Thoughts: **Analyzing `memfd_luo_put_folios` Error Handling and Folio Preservation** Okay, let's break this down. We're looking at `memfd_luo_put_folios`, specifically how it handles errors during folio preservation. The initial thought is to examine how the code cleans up folios if something goes wrong. First, I see the `err_restore` and `err_put` labels. The critical part is `memfd_luo_put_folios(folios_ser, nr_folios);`. I need to ensure that the error handling in `memfd_luo_put_folios` is correct when something goes wrong. Looking at the `memfd_luo_put_folios` function, the loop immediately catches my eye: `for (i = 0; i < nr_folios; i++)`. Good, `nr_folios` *starts* at zero, and the loop seems to iterate correctly, up to (but not including) the current value of `nr_folios`. It's reading the serialized folio data. Now, how does `nr_folios` get incremented? I remember it's within a loop where `memfd_luo_preserve_folio` is called. It *only* increments if the preservation is successful. Specifically, in the failure case, `nr_folios` is *not* incremented if `memfd_luo_preserve_folio` returns an error, thus the number is consistent. This is important to ensure consistency during the cleanup. The `memfd_luo_put_folios` function will only operate on the successfully preserved folios. This seems correct. Then I am thinking, what if other steps fail? Is there something missing? Let's look at `shmem_get_folio` and the unlikely case of `!folio_is_longterm_pinnable(folio)`. I'm recalling that `folio_unlock(folio)` happens *before* the check, and no changes to `folios_ser` happen. Then I saw `vrealloc` and `kho_preserve_vmalloc`. Ah, that's where the folio array might get reallocated! If `vrealloc` fails, `shrunk` will be NULL, and it handles it correctly. But `kho_preserve_vmalloc`... that's where the magic happens, or at least the critical part. My mind says that the `kho_vmalloc` is used to preserve the physical pages across a kexec. Ok, so the key thing is: even on failure, the `nr_folios` value accurately represents the number of successfully preserved folios. And `memfd_luo_put_folios` iterates over *exactly* those preserved folios. Let's look at `memfd_luo_retrieve_folios`, is it consistent? In `memfd_luo_retrieve_folios`, I see: ```c static int memfd_luo_retrieve_folios(struct file *file, struct memfd_luo_folio_ser *folios_ser, u64 nr_folios) ``` and within `memfd_luo_retrieve`, I see that `folios_ser` is obtained by `phys_to_virt(kho_vmalloc_to_phys(&ser->folios));`. It retrieves `nr_folios` elements, which is the serialized folios that were persisted. Looks good, the data is retrieved. Now, a crucial question, is this exposed to user space? I need to check the interface. Is there an ioctl or syscall? I need to understand what `liveupdate` and `memfd_luo` are for. Time to go back to `mm/memfd_luo.c` and check the surrounding code, especially around the first 100 lines, to see how it's exposed to user space! |
| 92/3 | 2026/10/28 02:18 | tool | grepper |
0mArgs:{
"Expression": "memfd_luo",
"PathPrefixes": [
"mm/"
]
}Results: {
"Output": "mm/Makefile=103=obj-$(CONFIG_PAGE_COUNTER) += page_counter.o\nmm/Makefile:104:obj-$(CONFIG_LIVEUPDATE_MEMFD) += memfd_luo.o\nmm/Makefile-105-obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o\n--\nmm/memfd_luo.c-91-\nmm/memfd_luo.c:92:static void memfd_luo_put_folios(const struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-93-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-97-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:98:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-99-\t\tstruct folio *folio;\n--\nmm/memfd_luo.c-122- */\nmm/memfd_luo.c:123:static int memfd_luo_migrate_folio(struct folio *folio)\nmm/memfd_luo.c-124-{\n--\nmm/memfd_luo.c-151-\nmm/memfd_luo.c:152:static int memfd_luo_preserve_folio(struct folio *folio,\nmm/memfd_luo.c:153:\t\t\t\t struct memfd_luo_folio_ser *pfolio)\nmm/memfd_luo.c-154-{\n--\nmm/memfd_luo.c-188-\nmm/memfd_luo.c:189:static int memfd_luo_preserve_folios(struct file *file,\nmm/memfd_luo.c-190-\t\t\t\t struct kho_vmalloc *kho_vmalloc,\nmm/memfd_luo.c:191:\t\t\t\t struct memfd_luo_folio_ser **out_folios_ser,\nmm/memfd_luo.c-192-\t\t\t\t u64 *nr_foliosp)\nmm/memfd_luo.c-193-{\nmm/memfd_luo.c:194:\tstruct memfd_luo_folio_ser *folios_ser, *shrunk;\nmm/memfd_luo.c-195-\tstruct inode *inode = file_inode(file);\n--\nmm/memfd_luo.c-253-\t\t\tfolio_unlock(folio);\nmm/memfd_luo.c:254:\t\t\terr = memfd_luo_migrate_folio(folio);\nmm/memfd_luo.c-255-\t\t\t/* Someone else might have it isolated, retry a bit. */\n--\nmm/memfd_luo.c-262-\nmm/memfd_luo.c:263:\t\terr = memfd_luo_preserve_folio(folio, \u0026folios_ser[nr_folios]);\nmm/memfd_luo.c-264-\t\tindex = folio_next_index(folio);\n--\nmm/memfd_luo.c-300-err_put:\nmm/memfd_luo.c:301:\tmemfd_luo_put_folios(folios_ser, nr_folios);\nmm/memfd_luo.c-302-\tvfree(folios_ser);\n--\nmm/memfd_luo.c-305-\nmm/memfd_luo.c:306:static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,\nmm/memfd_luo.c:307:\t\t\t\t\tstruct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-308-\t\t\t\t\tu64 nr_folios)\n--\nmm/memfd_luo.c-313-\tkho_unpreserve_vmalloc(kho_vmalloc);\nmm/memfd_luo.c:314:\tmemfd_luo_put_folios(folios_ser, nr_folios);\nmm/memfd_luo.c-315-\tvfree(folios_ser);\n--\nmm/memfd_luo.c-317-\nmm/memfd_luo.c:318:static int memfd_luo_preserve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-319-{\nmm/memfd_luo.c-320-\tstruct inode *inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:321:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c:322:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-323-\tu64 nr_folios, inode_size;\n--\nmm/memfd_luo.c-352-\nmm/memfd_luo.c:353:\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\nmm/memfd_luo.c-354-\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n--\nmm/memfd_luo.c-378-\nmm/memfd_luo.c:379:static int memfd_luo_freeze(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-380-{\nmm/memfd_luo.c:381:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-382-\n--\nmm/memfd_luo.c-396-\nmm/memfd_luo.c:397:static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-398-{\nmm/memfd_luo.c-399-\tstruct inode *inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:400:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-401-\n--\nmm/memfd_luo.c-409-\nmm/memfd_luo.c:410:\tmemfd_luo_unpreserve_folios(\u0026ser-\u003efolios, args-\u003eprivate_data,\nmm/memfd_luo.c-411-\t\t\t\t ser-\u003enr_folios);\n--\nmm/memfd_luo.c-416-\nmm/memfd_luo.c:417:static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-418-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-422-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:423:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-424-\t\tstruct folio *folio;\n--\nmm/memfd_luo.c-441-\nmm/memfd_luo.c:442:static void memfd_luo_finish(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-443-{\nmm/memfd_luo.c:444:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c:445:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-446-\n--\nmm/memfd_luo.c-463-\nmm/memfd_luo.c:464:\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\nmm/memfd_luo.c-465-\t\tvfree(folios_ser);\n--\nmm/memfd_luo.c-471-\nmm/memfd_luo.c:472:static int memfd_luo_retrieve_folios(struct file *file,\nmm/memfd_luo.c:473:\t\t\t\t struct memfd_luo_folio_ser *folios_ser,\nmm/memfd_luo.c-474-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-483-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:484:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-485-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-555-\tfor (long j = i + 1; j \u003c nr_folios; j++) {\nmm/memfd_luo.c:556:\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[j];\nmm/memfd_luo.c-557-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-572-\nmm/memfd_luo.c:573:static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)\nmm/memfd_luo.c-574-{\nmm/memfd_luo.c:575:\tstruct memfd_luo_folio_ser *folios_ser;\nmm/memfd_luo.c:576:\tstruct memfd_luo_ser *ser;\nmm/memfd_luo.c-577-\tstruct file *file;\n--\nmm/memfd_luo.c-616-\nmm/memfd_luo.c:617:\t\terr = memfd_luo_retrieve_folios(file, folios_ser, ser-\u003enr_folios);\nmm/memfd_luo.c-618-\t\tvfree(folios_ser);\n--\nmm/memfd_luo.c-634-\nmm/memfd_luo.c:635:static bool memfd_luo_can_preserve(struct liveupdate_file_handler *handler,\nmm/memfd_luo.c-636-\t\t\t\t struct file *file)\n--\nmm/memfd_luo.c-642-\nmm/memfd_luo.c:643:static unsigned long memfd_luo_get_id(struct file *file)\nmm/memfd_luo.c-644-{\n--\nmm/memfd_luo.c-647-\nmm/memfd_luo.c:648:static const struct liveupdate_file_ops memfd_luo_file_ops = {\nmm/memfd_luo.c:649:\t.freeze = memfd_luo_freeze,\nmm/memfd_luo.c:650:\t.finish = memfd_luo_finish,\nmm/memfd_luo.c:651:\t.retrieve = memfd_luo_retrieve,\nmm/memfd_luo.c:652:\t.preserve = memfd_luo_preserve,\nmm/memfd_luo.c:653:\t.unpreserve = memfd_luo_unpreserve,\nmm/memfd_luo.c:654:\t.can_preserve = memfd_luo_can_preserve,\nmm/memfd_luo.c:655:\t.get_id = memfd_luo_get_id,\nmm/memfd_luo.c-656-\t.owner = THIS_MODULE,\n--\nmm/memfd_luo.c-658-\nmm/memfd_luo.c:659:static struct liveupdate_file_handler memfd_luo_handler = {\nmm/memfd_luo.c:660:\t.ops = \u0026memfd_luo_file_ops,\nmm/memfd_luo.c-661-\t.compatible = MEMFD_LUO_FH_COMPATIBLE,\n--\nmm/memfd_luo.c-663-\nmm/memfd_luo.c:664:static int __init memfd_luo_init(void)\nmm/memfd_luo.c-665-{\nmm/memfd_luo.c:666:\tint err = liveupdate_register_file_handler(\u0026memfd_luo_handler);\nmm/memfd_luo.c-667-\n--\nmm/memfd_luo.c-676-}\nmm/memfd_luo.c:677:late_initcall(memfd_luo_init);\n"
} |
| 93/3 | 2026/10/28 02:18 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 39454 output: 37 thoughts: 27 Thoughts: Okay, let's dive into this. Here's my thought process on examining `memfd_luo_preserve` around line 320: **Analyzing `memfd_luo_preserve` for Resource Allocation** Right, let's zoom in on `memfd_luo_preserve` around line 320. My initial instinct is to pinpoint the exact memory allocation or resource management happening there. I need to understand what this function, or the surrounding code, is *doing* with system resources, particularly memory. Is it allocating new memory, perhaps using `mmap`, `malloc`, or a similar system call? Is it working with file descriptors, and if so, how? And critically, I need to know the context: what data structures is it operating on? What's the *purpose* of this allocation or operation? I'm looking for the "what" and the "why" related to resources. I'll need to examine the surrounding code to determine how this function integrates with the system and if any potential for inefficiencies exist. Understanding the context is key to optimizing this function or understanding what other systems may depend on it. |
| 94/3 | 2026/10/28 02:18 | tool | read-file |
0mArgs:{
"File": "mm/memfd_luo.c",
"FirstLine": 320,
"LineCount": 60
}Results: {
"Contents": " 320:\t\tstruct inode *inode = file_inode(args-\u003efile);\n 321:\t\tstruct memfd_luo_folio_ser *folios_ser;\n 322:\t\tstruct memfd_luo_ser *ser;\n 323:\t\tu64 nr_folios, inode_size;\n 324:\t\tint err = 0, seals;\n 325:\t\n 326:\t\tinode_lock(inode);\n 327:\t\n 328:\t\t/* Allocate the main serialization structure in preserved memory */\n 329:\t\tser = kho_alloc_preserve(sizeof(*ser));\n 330:\t\tif (IS_ERR(ser)) {\n 331:\t\t\terr = PTR_ERR(ser);\n 332:\t\t\tgoto err_unlock;\n 333:\t\t}\n 334:\t\n 335:\t\tseals = memfd_get_seals(args-\u003efile);\n 336:\t\tif (seals \u003c 0) {\n 337:\t\t\terr = seals;\n 338:\t\t\tgoto err_free_ser;\n 339:\t\t}\n 340:\t\n 341:\t\t/* Make sure the file only has the seals supported by this version. */\n 342:\t\tif (seals \u0026 ~MEMFD_LUO_ALL_SEALS) {\n 343:\t\t\terr = -EOPNOTSUPP;\n 344:\t\t\tgoto err_free_ser;\n 345:\t\t}\n 346:\t\n 347:\t\tser-\u003epos = args-\u003efile-\u003ef_pos;\n 348:\t\tinode_size = i_size_read(inode);\n 349:\t\n 350:\t\tser-\u003esize = inode_size;\n 351:\t\tser-\u003eseals = seals;\n 352:\t\n 353:\t\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\n 354:\t\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n 355:\t\tif (err)\n 356:\t\t\tgoto err_free_ser;\n 357:\t\n 358:\t\t/*\n 359:\t\t * All the folios in the file are now stable. Freeze the mapping to make\n 360:\t\t * sure new ones can't be added.\n 361:\t\t */\n 362:\t\tmapping_set_frozen(inode-\u003ei_mapping);\n 363:\t\n 364:\t\tser-\u003enr_folios = nr_folios;\n 365:\t\tinode_unlock(inode);\n 366:\t\n 367:\t\targs-\u003eprivate_data = folios_ser;\n 368:\t\targs-\u003eserialized_data = virt_to_phys(ser);\n 369:\t\n 370:\t\treturn 0;\n 371:\t\n 372:\terr_free_ser:\n 373:\t\tkho_unpreserve_free(ser);\n 374:\terr_unlock:\n 375:\t\tinode_unlock(inode);\n 376:\t\treturn err;\n 377:\t}\n 378:\t\n 379:\tstatic int memfd_luo_freeze(struct liveupdate_file_op_args *args)\n"
} |
| 95/3 | 2026/10/28 02:18 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 40607 output: 37 thoughts: 29 Thoughts: Okay, here's my take on those lines from `mm/memfd_luo.c`, as if I'm the one thinking it: **Digging into memfd_luo.c: Lines 378-440** Alright, let's zero in on lines 378 through 440 in `mm/memfd_luo.c`. This section's crucial, and I'm betting it deals with the core of the memory file descriptor implementation, probably involving some critical resource management or error handling. We're talking about a key component here, so it's time to refresh my understanding of how this memfd implementation interacts with the kernel's memory management. I need to understand what's happening at this level because these lines are likely involved in something significant, and I need to assess how it fits into the broader picture of how memfds are supposed to work. My goal here is to get a deeper sense of what this piece does in that file and to assess how robust the code is and what edge-cases or vulnerabilities might exist. |
| 96/3 | 2026/10/28 02:19 | tool | read-file |
0mArgs:{
"File": "mm/memfd_luo.c",
"FirstLine": 378,
"LineCount": 50
}Results: {
"Contents": " 378:\t\n 379:\tstatic int memfd_luo_freeze(struct liveupdate_file_op_args *args)\n 380:\t{\n 381:\t\tstruct memfd_luo_ser *ser;\n 382:\t\n 383:\t\tif (WARN_ON_ONCE(!args-\u003eserialized_data))\n 384:\t\t\treturn -EINVAL;\n 385:\t\n 386:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 387:\t\n 388:\t\t/*\n 389:\t\t * The pos might have changed since prepare. Everything else stays the\n 390:\t\t * same.\n 391:\t\t */\n 392:\t\tser-\u003epos = args-\u003efile-\u003ef_pos;\n 393:\t\n 394:\t\treturn 0;\n 395:\t}\n 396:\t\n 397:\tstatic void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)\n 398:\t{\n 399:\t\tstruct inode *inode = file_inode(args-\u003efile);\n 400:\t\tstruct memfd_luo_ser *ser;\n 401:\t\n 402:\t\tif (WARN_ON_ONCE(!args-\u003eserialized_data))\n 403:\t\t\treturn;\n 404:\t\n 405:\t\tinode_lock(inode);\n 406:\t\tmapping_clear_frozen(inode-\u003ei_mapping);\n 407:\t\n 408:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 409:\t\n 410:\t\tmemfd_luo_unpreserve_folios(\u0026ser-\u003efolios, args-\u003eprivate_data,\n 411:\t\t\t\t\t ser-\u003enr_folios);\n 412:\t\n 413:\t\tkho_unpreserve_free(ser);\n 414:\t\tinode_unlock(inode);\n 415:\t}\n 416:\t\n 417:\tstatic void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_ser,\n 418:\t\t\t\t\t u64 nr_folios)\n 419:\t{\n 420:\t\tu64 i;\n 421:\t\n 422:\t\tfor (i = 0; i \u003c nr_folios; i++) {\n 423:\t\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\n 424:\t\t\tstruct folio *folio;\n 425:\t\t\tphys_addr_t phys;\n 426:\t\n 427:\t\t\tif (!pfolio-\u003epfn)\n"
} |
| 97/3 | 2026/10/28 02:19 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 41611 output: 37 thoughts: 26 Thoughts: Okay, here's my attempt at summarizing the thought process, as requested, aimed at an expert audience and in the first person: **Diving into `memfd_luo_retrieve` and `memfd_luo_retrieve_folios`** Alright, time to get my hands dirty. I need to take a close look at `memfd_luo_retrieve` and `memfd_luo_retrieve_folios`. My initial hunch is this likely deals with retrieval from a memory file descriptor, probably related to the LUO (likely Large Unified Object) subsystem, or potentially some kind of shared memory management. I'm immediately thinking about how this interacts with the page cache, how it handles potential coherence issues if there are multiple writers or readers, and whether there's any clever use of folios to optimize memory management. I'm keen to see if this is handling direct I/O, or if it's falling back on traditional buffered I/O, since that drastically changes the performance profile. My primary questions here are: how's the data actually *stored*? Is it in a contiguous region, or are there clever tricks with page tables or something more esoteric to make this work? I need to look into how this behaves in terms of memory pinning and what the implications are for virtual memory pressure. Let's see if this supports partial retrievals or if we're forced to read everything in one shot. Time to crack open the code and start digging! |
| 98/3 | 2026/10/28 02:21 | tool | read-file |
0mArgs:{
"File": "mm/memfd_luo.c",
"FirstLine": 470,
"LineCount": 80
}Results: {
"Contents": " 470:\t}\n 471:\t\n 472:\tstatic int memfd_luo_retrieve_folios(struct file *file,\n 473:\t\t\t\t\t struct memfd_luo_folio_ser *folios_ser,\n 474:\t\t\t\t\t u64 nr_folios)\n 475:\t{\n 476:\t\tstruct inode *inode = file_inode(file);\n 477:\t\tstruct address_space *mapping = inode-\u003ei_mapping;\n 478:\t\tstruct folio *folio;\n 479:\t\tlong npages, nr_added_pages = 0;\n 480:\t\tint err = -EIO;\n 481:\t\tlong i;\n 482:\t\n 483:\t\tfor (i = 0; i \u003c nr_folios; i++) {\n 484:\t\t\tconst struct memfd_luo_folio_ser *pfolio = \u0026folios_ser[i];\n 485:\t\t\tphys_addr_t phys;\n 486:\t\t\tu64 index;\n 487:\t\t\tint flags;\n 488:\t\n 489:\t\t\tif (!pfolio-\u003epfn)\n 490:\t\t\t\tcontinue;\n 491:\t\n 492:\t\t\tphys = PFN_PHYS(pfolio-\u003epfn);\n 493:\t\t\tfolio = kho_restore_folio(phys);\n 494:\t\t\tif (!folio) {\n 495:\t\t\t\tpr_err(\"Unable to restore folio at physical address: %llx\\n\",\n 496:\t\t\t\t phys);\n 497:\t\t\t\terr = -EIO;\n 498:\t\t\t\tgoto put_folios;\n 499:\t\t\t}\n 500:\t\t\tindex = pfolio-\u003eindex;\n 501:\t\t\tflags = pfolio-\u003eflags;\n 502:\t\n 503:\t\t\t/* Set up the folio for insertion. */\n 504:\t\t\t__folio_set_locked(folio);\n 505:\t\t\t__folio_set_swapbacked(folio);\n 506:\t\n 507:\t\t\terr = mem_cgroup_charge(folio, NULL, mapping_gfp_mask(mapping));\n 508:\t\t\tif (err) {\n 509:\t\t\t\tpr_err(\"shmem: failed to charge folio index %ld: %d\\n\",\n 510:\t\t\t\t i, err);\n 511:\t\t\t\tgoto unlock_folio;\n 512:\t\t\t}\n 513:\t\n 514:\t\t\terr = shmem_add_to_page_cache(folio, mapping, index, NULL,\n 515:\t\t\t\t\t\t mapping_gfp_mask(mapping));\n 516:\t\t\tif (err) {\n 517:\t\t\t\tpr_err(\"shmem: failed to add to page cache folio index %ld: %d\\n\",\n 518:\t\t\t\t i, err);\n 519:\t\t\t\tgoto unlock_folio;\n 520:\t\t\t}\n 521:\t\n 522:\t\t\tif (flags \u0026 MEMFD_LUO_FOLIO_UPTODATE)\n 523:\t\t\t\tfolio_mark_uptodate(folio);\n 524:\t\t\tif (flags \u0026 MEMFD_LUO_FOLIO_DIRTY)\n 525:\t\t\t\tfolio_mark_dirty(folio);\n 526:\t\n 527:\t\t\tnpages = folio_nr_pages(folio);\n 528:\t\t\terr = shmem_inode_acct_blocks(inode, npages);\n 529:\t\t\tif (err) {\n 530:\t\t\t\tpr_err(\"shmem: failed to account folio index %ld(%ld pages): %d\\n\",\n 531:\t\t\t\t i, npages, err);\n 532:\t\t\t\tgoto remove_from_cache;\n 533:\t\t\t}\n 534:\t\n 535:\t\t\tnr_added_pages += npages;\n 536:\t\t\tfolio_add_lru(folio);\n 537:\t\t\tfolio_unlock(folio);\n 538:\t\t\tfolio_put(folio);\n 539:\t\t}\n 540:\t\n 541:\t\tshmem_recalc_inode(inode, nr_added_pages, 0);\n 542:\t\n 543:\t\treturn 0;\n 544:\t\n 545:\tremove_from_cache:\n 546:\t\tfilemap_remove_folio(folio);\n 547:\tunlock_folio:\n 548:\t\tfolio_unlock(folio);\n 549:\t\tfolio_put(folio);\n"
} |
| 99/3 | 2026/10/28 02:21 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 43153 output: 37 thoughts: 14 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and rendered in the first person: **Analyzing `memfd_luo_retrieve`** Alright, let's dive in and dissect `memfd_luo_retrieve`. My initial reaction is to think critically about this function's purpose within the larger context. Given its name, I'm already formulating some hypotheses about memory file descriptors and data retrieval. I'm immediately wondering about the potential implications for security – are there any risks of memory leaks, data corruption, or even unauthorized access? What's the error handling like? How does it interact with the underlying kernel memory management? Is it thread-safe? I'm picturing the likely data structures and control flow at play here – is this a simple read operation, or a more complex scheme involving caching, synchronization primitives, or even memory mapping? I need to understand its relationship to any existing mechanisms that are being used to manage memory. |
| 100/3 | 2026/10/28 02:22 | tool | read-file |
0mArgs:{
"File": "mm/memfd_luo.c",
"FirstLine": 570,
"LineCount": 55
}Results: {
"Contents": " 570:\t\treturn err;\n 571:\t}\n 572:\t\n 573:\tstatic int memfd_luo_retrieve(struct liveupdate_file_op_args *args)\n 574:\t{\n 575:\t\tstruct memfd_luo_folio_ser *folios_ser;\n 576:\t\tstruct memfd_luo_ser *ser;\n 577:\t\tstruct file *file;\n 578:\t\tint err;\n 579:\t\n 580:\t\tser = phys_to_virt(args-\u003eserialized_data);\n 581:\t\tif (!ser)\n 582:\t\t\treturn -EINVAL;\n 583:\t\n 584:\t\t/* Make sure the file only has seals supported by this version. */\n 585:\t\tif (ser-\u003eseals \u0026 ~MEMFD_LUO_ALL_SEALS) {\n 586:\t\t\terr = -EOPNOTSUPP;\n 587:\t\t\tgoto free_ser;\n 588:\t\t}\n 589:\t\n 590:\t\t/*\n 591:\t\t * The seals are preserved. Allow sealing here so they can be added\n 592:\t\t * later.\n 593:\t\t */\n 594:\t\tfile = memfd_alloc_file(\"\", MFD_ALLOW_SEALING);\n 595:\t\tif (IS_ERR(file)) {\n 596:\t\t\tpr_err(\"failed to setup file: %pe\\n\", file);\n 597:\t\t\terr = PTR_ERR(file);\n 598:\t\t\tgoto free_ser;\n 599:\t\t}\n 600:\t\n 601:\t\terr = memfd_add_seals(file, ser-\u003eseals);\n 602:\t\tif (err) {\n 603:\t\t\tpr_err(\"failed to add seals: %pe\\n\", ERR_PTR(err));\n 604:\t\t\tgoto put_file;\n 605:\t\t}\n 606:\t\n 607:\t\tvfs_setpos(file, ser-\u003epos, MAX_LFS_FILESIZE);\n 608:\t\ti_size_write(file_inode(file), ser-\u003esize);\n 609:\t\n 610:\t\tif (ser-\u003enr_folios) {\n 611:\t\t\tfolios_ser = kho_restore_vmalloc(\u0026ser-\u003efolios);\n 612:\t\t\tif (!folios_ser) {\n 613:\t\t\t\terr = -EINVAL;\n 614:\t\t\t\tgoto put_file;\n 615:\t\t\t}\n 616:\t\n 617:\t\t\terr = memfd_luo_retrieve_folios(file, folios_ser, ser-\u003enr_folios);\n 618:\t\t\tvfree(folios_ser);\n 619:\t\t\tif (err)\n 620:\t\t\t\tgoto put_file;\n 621:\t\t}\n 622:\t\n 623:\t\targs-\u003efile = file;\n 624:\t\tkho_restore_free(ser);\n"
} |
| 101/3 | 2026/10/28 02:22 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 44197 output: 31 thoughts: 405 Thoughts: **Analyzing Potential Vulnerabilities in memfd_luo_preserve_folios** Okay, let's break this down. I'm looking at `memfd_luo_preserve_folios` and something immediately jumps out. We're allocating `folios_ser` based on `max_folios`, which is the ceiling of `size / PAGE_SIZE`. Then, we consider the case where `nr_folios` might be *less* than `max_folios`. This could happen due to multi-order folios or if `vrealloc` fails during the process. The crux of the matter is this: If `vrealloc` fails, `folios_ser` will still have space for `max_folios` but only the first `nr_folios` entries will be populated by `memfd_luo_preserve_folio`. We set `ser->nr_folios = nr_folios;`. But here's the critical point: when these folios are restored in a future kernel using `memfd_luo_retrieve_folios`, or discarded, or unpreserved, or put, the code *only* iterates up to `ser->nr_folios - 1`. So, it never reads past the initialized elements. That means if `nr_folios < max_folios`, we're not touching those extra entries. This looks safe. But, I need to be absolutely sure. This could lead to information leaks or other problems if there's any implicit behavior I'm missing. My next step? Verify that *nothing* in this patch, no `struct memfd_luo_folio_ser`, `struct memfd_luo_ser`, or anything related is ever copied to user space! It seems safe on the surface, but I can't leave it to chance. I'll grep for any `memfd_luo_`, `kho_`, or `liveupdate_file_` code being copied to userspace and put this whole idea to rest. |
| 102/3 | 2026/10/28 02:23 | tool | grepper |
0mError:no matches Args: {
"Expression": "copy_to_user.*memfd|copy_to_user.*liveupdate"
}Results: {
"error": "no matches"
} |
| 103/3 | 2026/10/28 02:23 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 45068 output: 22 thoughts: 24 Thoughts: Here's my thought process, as requested: **Investigating LiveUpdate Implementation** Okay, so I need to get a handle on how `liveupdate_file_handler` or just plain `liveupdate` are being used within this system. I need to understand the call structure, the integration points. My instinct is to trace their usage, to map the function calls and the data flows associated with it. I need to know where these elements are defined, where they are called from, and what other modules or functions they interact with. I'll start with a code search. This kind of mapping will give me a clear picture of how this live update mechanism is intended to function. I'll be looking for both direct calls and any indirect invocations through function pointers or similar mechanisms. It’s all about tracing the execution path and identifying any potential areas of concern or opportunity for optimization. Time to dig in and get a view of the broader architectural context. |
| 104/3 | 2026/10/28 02:24 | tool | grepper |
0mArgs:{
"Expression": "liveupdate_register_file_handler"
}Results: {
"Output": "include/linux/liveupdate.h=234=int liveupdate_reboot(void);\ninclude/linux/liveupdate.h-235-\ninclude/linux/liveupdate.h:236:int liveupdate_register_file_handler(struct liveupdate_file_handler *fh);\ninclude/linux/liveupdate.h-237-void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh);\n--\ninclude/linux/liveupdate.h=257=static inline int liveupdate_reboot(void)\n--\ninclude/linux/liveupdate.h-261-\ninclude/linux/liveupdate.h:262:static inline int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)\ninclude/linux/liveupdate.h-263-{\n--\nkernel/liveupdate/luo_file.c=855=void luo_file_set_destroy(struct luo_file_set *file_set)\n--\nkernel/liveupdate/luo_file.c-862-/**\nkernel/liveupdate/luo_file.c:863: * liveupdate_register_file_handler - Register a file handler with LUO.\nkernel/liveupdate/luo_file.c-864- * @fh: Pointer to a caller-allocated \u0026struct liveupdate_file_handler.\n--\nkernel/liveupdate/luo_file.c-873- */\nkernel/liveupdate/luo_file.c:874:int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)\nkernel/liveupdate/luo_file.c-875-{\n--\nkernel/liveupdate/luo_file.c-917- * Unregisters the file handler from the liveupdate core. This function\nkernel/liveupdate/luo_file.c:918: * reverses the operations of liveupdate_register_file_handler().\nkernel/liveupdate/luo_file.c-919- */\n--\nmm/memfd_luo.c=664=static int __init memfd_luo_init(void)\nmm/memfd_luo.c-665-{\nmm/memfd_luo.c:666:\tint err = liveupdate_register_file_handler(\u0026memfd_luo_handler);\nmm/memfd_luo.c-667-\n"
} |
| 105/3 | 2026/10/28 02:24 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 45907 output: 29 thoughts: 27 Thoughts: Here's my take on the thought process, as requested: **Diving into the Live Update File Handler** Alright, I need to get a better handle on how the live update file handler is actually *triggered* in this system. My instinct tells me the place to start is `kernel/liveupdate/luo_file.c`. That file name strongly suggests it's the core of the liveupdate process handling files, so it's the logical starting point for tracing the call path. Let's see how the liveupdate routines are invoked within that context and how the file interaction is orchestrated. Hopefully, I can pinpoint the crucial entry points and understand the control flow. |
| 106/3 | 2026/10/28 02:25 | tool | grepper |
0mArgs:{
"Expression": "ops-\u003epreserve",
"PathPrefixes": [
"kernel/liveupdate/"
]
}Results: {
"Output": "kernel/liveupdate/luo_file.c=230=int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)\n--\nkernel/liveupdate/luo_file.c-287-\targs.file = file;\nkernel/liveupdate/luo_file.c:288:\terr = fh-\u003eops-\u003epreserve(\u0026args);\nkernel/liveupdate/luo_file.c-289-\tif (err)\n--\nkernel/liveupdate/luo_file.c=874=int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)\n--\nkernel/liveupdate/luo_file.c-882-\t/* Sanity check that all required callbacks are set */\nkernel/liveupdate/luo_file.c:883:\tif (!fh-\u003eops-\u003epreserve || !fh-\u003eops-\u003eunpreserve || !fh-\u003eops-\u003eretrieve ||\nkernel/liveupdate/luo_file.c-884-\t !fh-\u003eops-\u003efinish || !fh-\u003eops-\u003ecan_preserve) {\n--\nkernel/liveupdate/luo_flb.c=107=static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)\n--\nkernel/liveupdate/luo_flb.c-119-\t\t\targs.flb = flb;\nkernel/liveupdate/luo_flb.c:120:\t\t\terr = flb-\u003eops-\u003epreserve(\u0026args);\nkernel/liveupdate/luo_flb.c-121-\t\t\tif (err) {\n--\nkernel/liveupdate/luo_flb.c=398=int liveupdate_register_flb(struct liveupdate_file_handler *fh,\n--\nkernel/liveupdate/luo_flb.c-409-\nkernel/liveupdate/luo_flb.c:410:\tif (WARN_ON(!flb-\u003eops-\u003epreserve || !flb-\u003eops-\u003eunpreserve ||\nkernel/liveupdate/luo_flb.c-411-\t\t !flb-\u003eops-\u003eretrieve || !flb-\u003eops-\u003efinish)) {\n"
} |
| 107/3 | 2026/10/28 02:25 | llm | kmsan-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 46649 output: 411 thoughts: 3482 Thoughts: **KMSAN Assessment: Liveupdate File Preservation Patch** Alright, let's break this down. We're looking at a patch that generalizes the concept of freezing page cache mappings, originally specific to shmem, and applying it across the board, especially for the live update functionality in `memfd_luo`. The patch introduces `AS_FROZEN` as a general address space flag and utilizes it to prevent modifications to the page cache during kexec. My primary focus here is to critically assess whether this change necessitates a KMSAN (Kernel Memory Sanitizer) run. First, I need to thoroughly re-examine the criteria for KMSAN. The critical rule states that we ONLY need KMSAN if the patch introduces risks that KASAN or other standard bug detectors *won't* catch. This means uninitialized memory usage *that can't be detected by those tools*. So, I need to methodically check these critical areas: 1. **Kernel Structures to Userspace:** This is a red flag. Does the patch introduce, modify, or send kernel data structures to userspace via `copy_to_user`, `put_user`, netlink, etc.? The patch does not touch *any* of those! The serialized data, particularly the `struct memfd_luo_folio_ser` and associated folio information, are stored *within* the kernel for handover to the next kernel image. User space doesn't see those serialized structures. 2. **Conditional Logic & Uninitialized Variables:** Does the patch introduce control flow paths dependent on uninitialized data? The `mapping_frozen` check, and other similar checks, only depend on `mapping->flags`, which is guaranteed to be initialized. The same is true for variables used within the preservation and migration logic (`nr_folios`, `folios_ser`). The code diligently initializes all fields in `struct memfd_luo_folio_ser` before their use. The initialization of control structures (migration targets, lists) is straightforward and complete. All seems good. 3. **Complex Data Structures & Uninitialized Fields:** Does the patch allocate and initialize complex structures where uninitialized fields could later be read? I need to analyze `folios_ser`, which is dynamically resized during the preservation step. `folios_ser` elements are explicitly initialized, even if the realloc fails. The code meticulously bounds all reads using the `nr_folios` counter, avoiding out-of-bounds access. The struct has no padding. 4. **Bounds Checks & Uninitialized Bytes:** Does this introduce opportunities to access uninitialized bytes due to faulty bounds checks or other logic? Freezing a page cache mapping via the `AS_FROZEN` flag does not allow access to uninitialized bytes of existing buffers. The freeze mechanism functions as a safeguard. It enforces a "no modifications" state, returning `-EBUSY` when something attempts to modify a frozen mapping. Existing pages are still accessible and usable, but there is no new initialization being done. So, where are the risks? * **Locking and Concurrency:** Potentially, race conditions, deadlocks, and lock order inversions could happen between setting and unsetting `AS_FROZEN` and file operations that might interact with the page cache. Those are detected by LOCKDEP and concurrency testing. * **Reference Counting and Folio Leaks:** Mistakes in folio reference counting within the `memfd_luo_preserve_folios()` or `memfd_luo_migrate_folio()` functions are likely. These would cause refcount imbalance errors or use-after-free, which KASAN, kernel refcount assertions, and standard sanity checks should catch. * **Page Cache State Invariants:** The patch introduces new calls to `WARN_ON_ONCE` and `VM_WARN_ON_ONCE_FOLIO`. However, these are triggered if invariants are violated and are there to detect bugs. * **Memory Leaks:** Errors during eviction or truncation of a frozen mapping could lead to memory leaks. KMEMLEAK should detect. My final judgment: there are no uninitialized memory bugs or kernel-to-user info leaks requiring KMSAN. The risks involve locking/concurrency, refcounting/UAF, page cache invariants, and memory leaks. These are areas well-handled by LOCKDEP, KASAN, KMEMLEAK, and standard kernel asserts. Therefore, `NeedsKMSAN = false`. |
| 108/3 | 2026/10/28 02:26 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch series introduces a generic address_space flag (AS_FROZEN) to prevent modifications to the page cache (folio addition, deletion, migration, splitting, collapsing, truncation) and refactors folio preservation in mm/memfd_luo.c for live updates across kexec.\n\nAnalysis of sanitizers:\n1. KMSAN applicability:\n- The patch does not expose any uninitialized memory to user space via copy_to_user, put_user, netlink, ioctl, or socket interfaces.\n- The structures modified/added (such as struct memfd_luo_folio_ser and struct migration_target_control) are fully initialized before use. The serialization array folios_ser has every element populated sequentially with all fields (pfn, flags, index) set, and all subsequent iterations and cleanup operations strictly bound access to the initialized count (nr_folios).\n- Adding checks for mapping_frozen() simply causes page cache operations (such as write_begin, split, collapse, migrate, remove) to safely fail early with -EBUSY or SCAN_FAIL. No conditional logic branches on uninitialized memory, nor does it allow reading uninitialized bytes from existing buffers.\n\n2. KASAN and other debugging tools:\n- The risks introduced by this patch involve concurrency and synchronization (lock ordering between i_pages xa_lock and inode locks), page cache state invariants, folio migration logic, and folio reference counting (isolating, pinning, and putting folios).\n- These bugs (such as deadlocks, refcounting leaks, use-after-free, or invalid memory accesses) are fully covered by standard KASAN, LOCKDEP, and kernel page asserts (VM_BUG_ON_FOLIO / VM_WARN_ON_ONCE).\n\nTherefore, a dedicated KMSAN fuzzing session is not justified.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch series introduces a generic address_space flag (AS_FROZEN) to prevent modifications to the page cache (folio addition, deletion, migration, splitting, collapsing, truncation) and refactors folio preservation in mm/memfd_luo.c for live updates across kexec.\n\nAnalysis of sanitizers:\n1. KMSAN applicability:\n- The patch does not expose any uninitialized memory to user space via copy_to_user, put_user, netlink, ioctl, or socket interfaces.\n- The structures modified/added (such as struct memfd_luo_folio_ser and struct migration_target_control) are fully initialized before use. The serialization array folios_ser has every element populated sequentially with all fields (pfn, flags, index) set, and all subsequent iterations and cleanup operations strictly bound access to the initialized count (nr_folios).\n- Adding checks for mapping_frozen() simply causes page cache operations (such as write_begin, split, collapse, migrate, remove) to safely fail early with -EBUSY or SCAN_FAIL. No conditional logic branches on uninitialized memory, nor does it allow reading uninitialized bytes from existing buffers.\n\n2. KASAN and other debugging tools:\n- The risks introduced by this patch involve concurrency and synchronization (lock ordering between i_pages xa_lock and inode locks), page cache state invariants, folio migration logic, and folio reference counting (isolating, pinning, and putting folios).\n- These bugs (such as deadlocks, refcounting leaks, use-after-free, or invalid memory accesses) are fully covered by standard KASAN, LOCKDEP, and kernel page asserts (VM_BUG_ON_FOLIO / VM_WARN_ON_ONCE).\n\nTherefore, a dedicated KMSAN fuzzing session is not justified.",
"NeedsKMSAN": false
} |
| Total Calls | Total Tokens | Avg Tokens | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|
| Total Calls | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|