AI Trajectory

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Seq	Timestamp	Type	Name	Duration
0/0	2026/10/14 08:43	flow	patch-triage	6m Args: null Results: { "EnableConfigs": [ "LIVEUPDATE_MEMFD", "LIVEUPDATE", "KEXEC_HANDOVER", "KEXEC_HANDOVER_ENABLE_DEFAULT", "TMPFS_POSIX_ACL", "MEMFD_CREATE", "TMPFS" ], "FocusSymbols": [ "memfd_luo_preserve", "memfd_luo_freeze", "memfd_luo_unfreeze", "memfd_luo_retrieve", "memfd_luo_finish", "memfd_luo_can_preserve", "memfd_add_seals", "shmem_set_acl" ], "KMSANReasoning": "The patch series updates memfd Live Update Orchestration (LUO) and shmem to preserve exact execute permission bits (user/group/other) across kexec reboots (supporting F_SEAL_EXEC), and freezes the seal/mode state during liveupdate to prevent divergence.\n\nAnalysis with respect to memory sanitizers:\n1. No uninitialized memory or info-leak risks:\n - The serialization record `struct memfd_luo_ser` is allocated via `kho_alloc_preserve()`, which internally uses `folio_alloc()` with `__GFP_ZERO`, ensuring all fields and padding are zero-initialized.\n - All newly added local variables (`flags`, `mode`, `folios_ser`) are explicitly initialized before use.\n - The serialized structure is exchanged internally between kernels during kexec handover (KHO) and is not copied to userspace. No data structures or padding are exposed to userspace via `copy_to_user`, ioctls, or netlink.\n2. KASAN/LOCKDEP applicability:\n - Any potential issues introduced by this patch revolve around concurrency/locking (`shmem_seal_state_frozen` lock discipline, inode lock serialization), file reference handling (`fput`), or folio lifetime management (`memfd_luo_discard_folios`), which are covered by standard KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nTherefore, this patch series does not introduce uninitialized memory read risks or kernel-to-user info-leaks, and a dedicated KMSAN session is not required.", "NeedsKMSAN": false, "Reasoning": "The patch modifies the Live Update Orchestrator (LUO) support for memfd and shmem/tmpfs. It introduces logic to preserve user/group/other execute permission bits and seal state across kexec live update transitions. It adds seal state freezing checks in memfd_add_seals() and shmem_setattr(), introduces shmem_set_acl() to prevent ACL modifications from diverging execution permissions after snapshotting, and implements unfreeze/error rollback handling in memfd_luo.c. These changes touch reachable core memory management and file system logic accessible from userspace.", "WorthFuzzing": true }
1/1	2026/10/14 08:43	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit b3d3d95b3632992db943db5e3203c4584c36d58d\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Oct 14 08:43:46 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h\nindex 08b10fea2afc8..f773dd95401d2 100644\n--- a/include/linux/kho/abi/memfd.h\n+++ b/include/linux/kho/abi/memfd.h\n@@ -87,7 +87,29 @@ struct memfd_luo_ser {\n \tstruct kho_vmalloc folios;\n } __packed;\n \n+/\n+ The execute permission bits are packed in user/group/other order. A record\n+ * with none of these flags set is restored without execute permissions, which\n+ * is also the safe interpretation for records written before these flags\n+ * existed.\n+ /\n+#define MEMFD_LUO_FL_EXEC_USR\t\tBIT(0)\n+#define MEMFD_LUO_FL_EXEC_GRP\t\tBIT(1)\n+#define MEMFD_LUO_FL_EXEC_OTH\t\tBIT(2)\n+#define MEMFD_LUO_FL_EXEC_MASK\t\t(MEMFD_LUO_FL_EXEC_USR \| \\\n+\t\t\t\t\t MEMFD_LUO_FL_EXEC_GRP \| \\\n+\t\t\t\t\t MEMFD_LUO_FL_EXEC_OTH)\n+#define MEMFD_LUO_ALL_FLAGS\t\tMEMFD_LUO_FL_EXEC_MASK\n+\n / The compatibility string for memfd file handler /\n-#define MEMFD_LUO_FH_COMPATIBLE\t\"memfd-v2\"\n+#define MEMFD_LUO_FH_COMPATIBLE\t\t\"memfd-v3\"\n+/\n+ * Records written before the execute-bit flags existed. They carry no flag\n+ * bits and are restored without execute permissions: the flags cannot tell\n+ * \"the execute bits were clear\" and \"the writer did not know about the flags\"\n+ * apart, and restoring without them is the safe reading. The current kernel\n+ * still accepts these records but never writes them.\n+ /\n+#define MEMFD_LUO_FH_COMPATIBLE_V2\t\"memfd-v2\"\n \n #endif / _LINUX_KHO_ABI_MEMFD_H /\ndiff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h\nindex e729b9b0e38d4..40e1ce87c30e0 100644\n--- a/include/linux/shmem_fs.h\n+++ b/include/linux/shmem_fs.h\n@@ -32,6 +32,12 @@ struct swap_iocb;\n isn't directly visible to userspace.\n /\n #define SHMEM_F_MAPPING_FROZEN\tBIT(2)\n+/\n+ * Disallow changes to the seal set and execute bits captured by the final LUO\n+ * snapshot. This is set only for the reboot transition and is cleared if the\n+ * transition is rolled back.\n+ /\n+#define SHMEM_F_SEAL_STATE_FROZEN\tBIT(3)\n \n struct shmem_inode_info {\n \tspinlock_t\t\tlock;\n@@ -208,6 +214,20 @@ static inline void shmem_freeze(struct inode inode, bool freeze)\n \t\tSHMEM_I(inode)-\u003eflags \u0026= ~SHMEM_F_MAPPING_FROZEN;\n }\n \n+/* Must be called with inode lock taken exclusive. /\n+static inline void shmem_freeze_seal_state(struct inode inode, bool freeze)\n+{\n+\tif (freeze)\n+\t\tSHMEM_I(inode)-\u003eflags \|= SHMEM_F_SEAL_STATE_FROZEN;\n+\telse\n+\t\tSHMEM_I(inode)-\u003eflags \u0026= ~SHMEM_F_SEAL_STATE_FROZEN;\n+}\n+\n+static inline bool shmem_seal_state_frozen(struct inode inode)\n+{\n+\treturn SHMEM_I(inode)-\u003eflags \u0026 SHMEM_F_SEAL_STATE_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/memfd.c b/mm/memfd.c\nindex abe13b291ddc8..578ac31ed1a9e 100644\n--- a/mm/memfd.c\n+++ b/mm/memfd.c\n@@ -278,6 +278,12 @@ int memfd_add_seals(struct file file, unsigned int seals)\n \t\tgoto unlock;\n \t}\n \n+\t/ LUO has taken its final snapshot; do not let the seal set diverge. /\n+\tif (shmem_file(file) \u0026\u0026 shmem_seal_state_frozen(inode)) {\n+\t\terror = -EPERM;\n+\t\tgoto unlock;\n+\t}\n+\n \tif (file_seals \u0026 F_SEAL_SEAL) {\n \t\terror = -EPERM;\n \t\tgoto unlock;\ndiff --git a/mm/memfd_luo.c b/mm/memfd_luo.c\nindex 59de210bee5f9..f1f07d90f73d1 100644\n--- a/mm/memfd_luo.c\n+++ b/mm/memfd_luo.c\n@@ -50,6 +50,16 @@\n * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property\n * is maintained.\n \n+ Execute Permission Bits\n+ * The user, group, and other execute bits are preserved individually. This\n+ * is required to faithfully restore the state protected by ``F_SEAL_EXEC``.\n+ \n+ .. note::\n+ * A record written by an older kernel (``memfd-v2``) does not carry the\n+ * execute bits. It is restored without execute permissions, which is the\n+ * safe reading: an executable memfd preserved by such a kernel comes back\n+ * non-executable, and the next update records the exact state.\n+ \n Seals\n * File seals set on the memfd are preserved and re-applied on restore.\n * Only seals known to this LUO version (see ``MEMFD_LUO_ALL_SEALS``) may\n@@ -84,6 +94,35 @@\n \n #include \"internal.h\"\n \n+static void memfd_luo_record_exec_mode(struct memfd_luo_ser ser, umode_t mode)\n+{\n+\tu32 flags = 0;\n+\n+\tif (mode \u0026 0100)\n+\t\tflags \|= MEMFD_LUO_FL_EXEC_USR;\n+\tif (mode \u0026 0010)\n+\t\tflags \|= MEMFD_LUO_FL_EXEC_GRP;\n+\tif (mode \u0026 0001)\n+\t\tflags \|= MEMFD_LUO_FL_EXEC_OTH;\n+\n+\tser-\u003eflags \u0026= ~MEMFD_LUO_FL_EXEC_MASK;\n+\tser-\u003eflags \|= flags;\n+}\n+\n+static umode_t memfd_luo_restore_exec_mode(u32 flags)\n+{\n+\tumode_t mode = 0;\n+\n+\tif (flags \u0026 MEMFD_LUO_FL_EXEC_USR)\n+\t\tmode \|= 0100;\n+\tif (flags \u0026 MEMFD_LUO_FL_EXEC_GRP)\n+\t\tmode \|= 0010;\n+\tif (flags \u0026 MEMFD_LUO_FL_EXEC_OTH)\n+\t\tmode \|= 0001;\n+\n+\treturn mode;\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@@ -300,6 +339,14 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args args)\n \tser-\u003esize = inode_size;\n \tser-\u003eseals = seals;\n \n+\t/\n+\t F_SEAL_EXEC freezes each execute permission bit independently, so\n+\t * preserve the complete user/group/other execute mask. A record with no\n+\t * execute flags is restored without execute permissions, which is also\n+\t * the safe interpretation for records written before these flags existed.\n+\t /\n+\tmemfd_luo_record_exec_mode(ser, inode-\u003ei_mode);\n+\n \terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\n \t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n \tif (err)\n@@ -323,7 +370,9 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args args)\n \n static int memfd_luo_freeze(struct liveupdate_file_op_args args)\n {\n+\tstruct inode inode = file_inode(args-\u003efile);\n \tstruct memfd_luo_ser ser;\n+\tint seals;\n \n \tif (WARN_ON_ONCE(!args-\u003eserialized_data))\n \t\treturn -EINVAL;\n@@ -331,14 +380,47 @@ static int memfd_luo_freeze(struct liveupdate_file_op_args args)\n \tser = phys_to_virt(args-\u003eserialized_data);\n \n \t/\n-\t The pos might have changed since prepare. Everything else stays the\n-\t * same.\n+\t * The file is still usable between preserve() and freeze(), so its mode\n+\t * and seals can differ from the values recorded by preserve(). Take the\n+\t * final snapshot under the inode lock shared with memfd_add_seals(),\n+\t * shmem_setattr(), and shmem_set_acl(), then freeze those state fields\n+\t * before dropping the lock. This closes the window in which a later\n+\t * chmod(), ACL update, or F_ADD_SEALS could otherwise diverge from the\n+\t * state handed to the next kernel.\n \t /\n+\tinode_lock(inode);\n+\n+\tseals = memfd_get_seals(args-\u003efile);\n+\tif (seals \u003c 0) {\n+\t\tinode_unlock(inode);\n+\t\treturn seals;\n+\t}\n+\n+\t/ The file must not have gained seals that this version does not know. /\n+\tif (seals \u0026 ~MEMFD_LUO_ALL_SEALS) {\n+\t\tinode_unlock(inode);\n+\t\treturn -EOPNOTSUPP;\n+\t}\n+\n+\tmemfd_luo_record_exec_mode(ser, inode-\u003ei_mode);\n+\tser-\u003eseals = seals;\n \tser-\u003epos = args-\u003efile-\u003ef_pos;\n+\tshmem_freeze_seal_state(inode, true);\n+\n+\tinode_unlock(inode);\n \n \treturn 0;\n }\n \n+static void memfd_luo_unfreeze(struct liveupdate_file_op_args args)\n+{\n+\tstruct inode inode = file_inode(args-\u003efile);\n+\n+\tinode_lock(inode);\n+\tshmem_freeze_seal_state(inode, false);\n+\tinode_unlock(inode);\n+}\n+\n static void memfd_luo_unpreserve(struct liveupdate_file_op_args args)\n {\n \tstruct inode inode = file_inode(args-\u003efile);\n@@ -348,6 +430,7 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args args)\n \t\treturn;\n \n \tinode_lock(inode);\n+\tshmem_freeze_seal_state(inode, false);\n \tshmem_freeze(inode, false);\n \n \tser = phys_to_virt(args-\u003eserialized_data);\n@@ -384,9 +467,31 @@ static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser folios_se\n \t}\n }\n \n-static void memfd_luo_finish(struct liveupdate_file_op_args args)\n+/\n+ Release a preserved record: return its folios to the page allocator and free\n+ * the record itself. Only valid for records whose folios were never handed to\n+ * a file -- handing a folio to a file consumes its last reference, and\n+ * memfd_luo_discard_folios() would release it a second time.\n+ /\n+static void memfd_luo_release_ser(struct memfd_luo_ser ser)\n {\n \tstruct memfd_luo_folio_ser folios_ser;\n+\n+\tif (ser-\u003enr_folios) {\n+\t\tfolios_ser = kho_restore_vmalloc(\u0026ser-\u003efolios);\n+\t\tif (!folios_ser)\n+\t\t\tgoto out;\n+\n+\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\n+\t\tvfree(folios_ser);\n+\t}\n+\n+out:\n+\tkho_restore_free(ser);\n+}\n+\n+static void memfd_luo_finish(struct liveupdate_file_op_args args)\n+{\n \tstruct memfd_luo_ser ser;\n \n \t/\n@@ -401,17 +506,7 @@ static void memfd_luo_finish(struct liveupdate_file_op_args args)\n \tif (!ser)\n \t\treturn;\n \n-\tif (ser-\u003enr_folios) {\n-\t\tfolios_ser = kho_restore_vmalloc(\u0026ser-\u003efolios);\n-\t\tif (!folios_ser)\n-\t\t\tgoto out;\n-\n-\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\n-\t\tvfree(folios_ser);\n-\t}\n-\n-out:\n-\tkho_restore_free(ser);\n+\tmemfd_luo_release_ser(ser);\n }\n \n static int memfd_luo_retrieve_folios(struct file file,\n@@ -517,32 +612,55 @@ static int memfd_luo_retrieve_folios(struct file file,\n \n static int memfd_luo_retrieve(struct liveupdate_file_op_args args)\n {\n-\tstruct memfd_luo_folio_ser folios_ser;\n+\tstruct memfd_luo_folio_ser folios_ser = NULL;\n \tstruct memfd_luo_ser ser;\n \tstruct file file;\n+\tumode_t exec_mode;\n \tint err;\n \n \tser = phys_to_virt(args-\u003eserialized_data);\n \tif (!ser)\n \t\treturn -EINVAL;\n \n-\t/* Make sure the file only has seals supported by this version. /\n-\tif (ser-\u003eseals \u0026 ~MEMFD_LUO_ALL_SEALS) {\n+\t/ Make sure the record only contains state supported by this version. /\n+\tif ((ser-\u003eseals \u0026 ~MEMFD_LUO_ALL_SEALS) \|\|\n+\t (ser-\u003eflags \u0026 ~MEMFD_LUO_ALL_FLAGS)) {\n \t\terr = -EOPNOTSUPP;\n-\t\tgoto free_ser;\n+\t\tgoto release_ser;\n \t}\n \n \t/\n-\t * The seals are preserved. Allow sealing here so they can be added\n-\t * later.\n+\t * Restore the folio array before allocating the file. Once this succeeds,\n+\t * every later error path can release the preserved folios directly instead\n+\t * of allocating memory again while already handling a failure.\n \t /\n+\tif (ser-\u003enr_folios) {\n+\t\tfolios_ser = kho_restore_vmalloc(\u0026ser-\u003efolios);\n+\t\tif (!folios_ser) {\n+\t\t\t/ kho_restore_vmalloc() is not safe to retry after failure. /\n+\t\t\terr = -EINVAL;\n+\t\t\tgoto free_ser;\n+\t\t}\n+\t}\n+\n \tfile = memfd_alloc_file(\"\", MFD_ALLOW_SEALING);\n \tif (IS_ERR(file)) {\n \t\tpr_err(\"failed to setup file: %pe\\n\", file);\n \t\terr = PTR_ERR(file);\n-\t\tgoto free_ser;\n+\t\tgoto discard_folios;\n \t}\n \n+\t/\n+\t * Reproduce the exact execute mask before the seals are re-applied:\n+\t * F_SEAL_EXEC freezes each execute bit, and the W^X rule in\n+\t * memfd_add_seals() looks at the mode when deciding whether to imply the\n+\t * write seals. The fresh anonymous inode has not been published, so no\n+\t * other thread can observe this intermediate state.\n+\t /\n+\texec_mode = memfd_luo_restore_exec_mode(ser-\u003eflags);\n+\tfile-\u003ef_inode-\u003ei_mode \u0026= ~0111;\n+\tfile-\u003ef_inode-\u003ei_mode \|= exec_mode;\n+\n \terr = memfd_add_seals(file, ser-\u003eseals);\n \tif (err) {\n \t\tpr_err(\"failed to add seals: %pe\\n\", ERR_PTR(err));\n@@ -552,15 +670,12 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args args)\n \tvfs_setpos(file, ser-\u003epos, MAX_LFS_FILESIZE);\n \ti_size_write(file_inode(file), ser-\u003esize);\n \n-\tif (ser-\u003enr_folios) {\n-\t\tfolios_ser = kho_restore_vmalloc(\u0026ser-\u003efolios);\n-\t\tif (!folios_ser) {\n-\t\t\terr = -EINVAL;\n-\t\t\tgoto put_file;\n-\t\t}\n-\n-\t\terr = memfd_luo_retrieve_folios(file, folios_ser, ser-\u003enr_folios);\n+\tif (folios_ser) {\n+\t\t/* retrieve_folios() consumes every preserved data folio. /\n+\t\terr = memfd_luo_retrieve_folios(file, folios_ser,\n+\t\t\t\t\t\tser-\u003enr_folios);\n \t\tvfree(folios_ser);\n+\t\tfolios_ser = NULL;\n \t\tif (err)\n \t\t\tgoto put_file;\n \t}\n@@ -572,9 +687,18 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args args)\n \n put_file:\n \tfput(file);\n+discard_folios:\n+\tif (folios_ser) {\n+\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\n+\t\tvfree(folios_ser);\n+\t}\n free_ser:\n \tkho_restore_free(ser);\n \treturn err;\n+\n+release_ser:\n+\tmemfd_luo_release_ser(ser);\n+\treturn err;\n }\n \n static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler,\n@@ -582,7 +706,12 @@ static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler,\n {\n \tstruct inode inode = file_inode(file);\n \n-\treturn shmem_file(file) \u0026\u0026 !inode-\u003ei_nlink;\n+\t/\n+\t * shmem_kernel_file_setup() marks kernel-private files S_PRIVATE. In\n+\t * particular, SysV SHM updates SHMEM_I(inode)-\u003eflags under its IPC lock,\n+\t * which does not serialize with the inode lock used by LUO.\n+\t /\n+\treturn shmem_file(file) \u0026\u0026 !IS_PRIVATE(inode) \u0026\u0026 !inode-\u003ei_nlink;\n }\n \n static unsigned long memfd_luo_get_id(struct file file)\n@@ -592,6 +721,7 @@ static unsigned long memfd_luo_get_id(struct file file)\n \n static const struct liveupdate_file_ops memfd_luo_file_ops = {\n \t.freeze = memfd_luo_freeze,\n+\t.unfreeze = memfd_luo_unfreeze,\n \t.finish = memfd_luo_finish,\n \t.retrieve = memfd_luo_retrieve,\n \t.preserve = memfd_luo_preserve,\n@@ -606,15 +736,62 @@ static struct liveupdate_file_handler memfd_luo_handler = {\n \t.compatible = MEMFD_LUO_FH_COMPATIBLE,\n };\n \n+/\n+ * Reads records written before the execute-bit flags existed. Those have no\n+ * flag bits and are restored without execute permissions (see the note on\n+ * old records in the DOC section above). can_preserve() never claims a file,\n+ * so an outgoing preservation is always written by the handler above and\n+ * never as \"memfd-v2\".\n+ /\n+static bool memfd_luo_can_preserve_v2(struct liveupdate_file_handler handler,\n+\t\t\t\t struct file file)\n+{\n+\treturn false;\n+}\n+\n+static const struct liveupdate_file_ops memfd_luo_file_ops_v2 = {\n+\t.freeze = memfd_luo_freeze,\n+\t.unfreeze = memfd_luo_unfreeze,\n+\t.finish = memfd_luo_finish,\n+\t.retrieve = memfd_luo_retrieve,\n+\t.preserve = memfd_luo_preserve,\n+\t.unpreserve = memfd_luo_unpreserve,\n+\t.can_preserve = memfd_luo_can_preserve_v2,\n+\t.get_id = memfd_luo_get_id,\n+\t.owner = THIS_MODULE,\n+};\n+\n+static struct liveupdate_file_handler memfd_luo_handler_v2 = {\n+\t.ops = \u0026memfd_luo_file_ops_v2,\n+\t.compatible = MEMFD_LUO_FH_COMPATIBLE_V2,\n+};\n+\n static int __init memfd_luo_init(void)\n {\n-\tint err = liveupdate_register_file_handler(\u0026memfd_luo_handler);\n+\tint err;\n+\n+\terr = liveupdate_register_file_handler(\u0026memfd_luo_handler);\n+\tif (err) {\n+\t\tif (err != -EOPNOTSUPP) {\n+\t\t\tpr_err(\"Could not register luo filesystem handler: %pe\\n\",\n+\t\t\t ERR_PTR(err));\n+\t\t\treturn err;\n+\t\t}\n \n-\tif (err \u0026\u0026 err != -EOPNOTSUPP) {\n-\t\tpr_err(\"Could not register luo filesystem handler: %pe\\n\",\n-\t\t ERR_PTR(err));\n+\t\treturn 0;\n+\t}\n+\n+\terr = liveupdate_register_file_handler(\u0026memfd_luo_handler_v2);\n+\tif (err) {\n+\t\tliveupdate_unregister_file_handler(\u0026memfd_luo_handler);\n \n-\t\treturn err;\n+\t\tif (err != -EOPNOTSUPP) {\n+\t\t\tpr_err(\"Could not register the memfd-v2 record reader: %pe\\n\",\n+\t\t\t ERR_PTR(err));\n+\t\t\treturn err;\n+\t\t}\n+\n+\t\treturn 0;\n \t}\n \n \treturn 0;\ndiff --git a/mm/shmem.c b/mm/shmem.c\nindex b51f83c970bb3..55f4dbd429eb9 100644\n--- a/mm/shmem.c\n+++ b/mm/shmem.c\n@@ -1326,11 +1326,10 @@ static int shmem_setattr(struct mnt_idmap idmap,\n \tif (error)\n \t\treturn error;\n \n-\tif ((info-\u003eseals \u0026 F_SEAL_EXEC) \u0026\u0026 (attr-\u003eia_valid \u0026 ATTR_MODE)) {\n-\t\tif ((inode-\u003ei_mode ^ attr-\u003eia_mode) \u0026 0111) {\n-\t\t\treturn -EPERM;\n-\t\t}\n-\t}\n+\tif ((attr-\u003eia_valid \u0026 ATTR_MODE) \u0026\u0026\n+\t ((info-\u003eseals \u0026 F_SEAL_EXEC) \|\| shmem_seal_state_frozen(inode)) \u0026\u0026\n+\t ((inode-\u003ei_mode ^ attr-\u003eia_mode) \u0026 0111))\n+\t\treturn -EPERM;\n \n \tif (S_ISREG(inode-\u003ei_mode) \u0026\u0026 (attr-\u003eia_valid \u0026 ATTR_SIZE)) {\n \t\tloff_t oldsize = inode-\u003ei_size;\n@@ -1394,6 +1393,24 @@ static int shmem_setattr(struct mnt_idmap idmap,\n \treturn error;\n }\n \n+#ifdef CONFIG_TMPFS_POSIX_ACL\n+static int shmem_set_acl(struct mnt_idmap idmap, struct dentry dentry,\n+\t\t\t struct posix_acl acl, int type)\n+{\n+\tstruct inode inode = d_inode(dentry);\n+\n+\t/\n+\t * An access ACL can rewrite the inode's execute bits without going\n+\t * through shmem_setattr(). Once LUO has captured its final seal/mode\n+\t * snapshot, reject that alternate mutation path as well.\n+\t /\n+\tif (type == ACL_TYPE_ACCESS \u0026\u0026 shmem_seal_state_frozen(inode))\n+\t\treturn -EPERM;\n+\n+\treturn simple_set_acl(idmap, dentry, acl, type);\n+}\n+#endif\n+\n static void shmem_evict_inode(struct inode inode)\n {\n \tstruct shmem_inode_info info = SHMEM_I(inode);\n@@ -5156,7 +5173,9 @@ static const struct inode_operations shmem_inode_operations = {\n \t.setattr\t= shmem_setattr,\n #ifdef CONFIG_TMPFS_XATTR\n \t.listxattr\t= shmem_listxattr,\n-\t.set_acl\t= simple_set_acl,\n+#ifdef CONFIG_TMPFS_POSIX_ACL\n+\t.set_acl\t= shmem_set_acl,\n+#endif\n \t.fileattr_get\t= shmem_fileattr_get,\n \t.fileattr_set\t= shmem_fileattr_set,\n #endif\n@@ -5184,7 +5203,7 @@ static const struct inode_operations shmem_dir_inode_operations = {\n #endif\n #ifdef CONFIG_TMPFS_POSIX_ACL\n \t.setattr\t= shmem_setattr,\n-\t.set_acl\t= simple_set_acl,\n+\t.set_acl\t= shmem_set_acl,\n #endif\n };\n \n@@ -5195,7 +5214,7 @@ static const struct inode_operations shmem_special_inode_operations = {\n #endif\n #ifdef CONFIG_TMPFS_POSIX_ACL\n \t.setattr\t= shmem_setattr,\n-\t.set_acl\t= simple_set_acl,\n+\t.set_acl\t= shmem_set_acl,\n #endif\n };\n \ndiff --git a/tools/testing/selftests/liveupdate/luo_kexec_simple.c b/tools/testing/selftests/liveupdate/luo_kexec_simple.c\nindex d7ac1f3dc4cbc..30836043f894e 100644\n--- a/tools/testing/selftests/liveupdate/luo_kexec_simple.c\n+++ b/tools/testing/selftests/liveupdate/luo_kexec_simple.c\n@@ -1,4 +1,5 @@\n // SPDX-License-Identifier: GPL-2.0-only\n+#define _GNU_SOURCE\n \n /\n * Copyright (c) 2025, Google LLC.\n@@ -8,16 +9,211 @@\n * across a single kexec reboot.\n /\n \n+#include \u003cfcntl.h\u003e\n+#include \u003csys/ioctl.h\u003e\n+#include \u003csys/mman.h\u003e\n+#include \u003csys/stat.h\u003e\n+#include \u003cunistd.h\u003e\n+\n+#include \u003clinux/memfd.h\u003e\n+\n #include \"luo_test_utils.h\"\n \n+#ifndef F_SEAL_SHRINK\n+#define F_SEAL_SHRINK 0x0002\n+#endif\n+#ifndef F_SEAL_GROW\n+#define F_SEAL_GROW 0x0004\n+#endif\n+#ifndef F_SEAL_WRITE\n+#define F_SEAL_WRITE 0x0008\n+#endif\n+#ifndef F_SEAL_FUTURE_WRITE\n+#define F_SEAL_FUTURE_WRITE 0x0010\n+#endif\n+#ifndef F_SEAL_EXEC\n+#define F_SEAL_EXEC 0x0020\n+#endif\n+#ifndef MFD_NOEXEC_SEAL\n+#define MFD_NOEXEC_SEAL 0x0008U\n+#endif\n+\n+/\n+ * F_SEAL_EXEC implies the write seals when the memfd has execute bits (the\n+ * W^X rule in memfd_add_seals()), so a memfd that was chmod()ed to 0700\n+ * before F_SEAL_EXEC was added ends up with exactly this seal set.\n+ /\n+#define F_WX_SEALS\t(F_SEAL_EXEC \| F_SEAL_SHRINK \| F_SEAL_GROW \| \\\n+\t\t\t F_SEAL_WRITE \| F_SEAL_FUTURE_WRITE)\n+\n #define TEST_SESSION_NAME \"test-session\"\n #define TEST_MEMFD_TOKEN 0x1A\n+#define TEST_EXEC_MEMFD_TOKEN 0x1B\n+#define TEST_NX_MEMFD_TOKEN 0x1C\n #define TEST_MEMFD_DATA \"hello kexec world\"\n \n / Constants for the state-tracking mechanism, specific to this test file. /\n #define STATE_SESSION_NAME \"kexec_simple_state\"\n #define STATE_MEMFD_TOKEN 999\n \n+static void create_and_preserve_exec_memfd(int session_fd)\n+{\n+\tstruct liveupdate_session_preserve_fd arg = {\n+\t\t.size = sizeof(arg),\n+\t\t.token = TEST_EXEC_MEMFD_TOKEN,\n+\t};\n+\tint mfd, seals;\n+\n+\tmfd = memfd_create(\"exec-mode-test\", MFD_ALLOW_SEALING \| MFD_EXEC);\n+\tif (mfd \u003c 0) {\n+\t\t/ vm.memfd_noexec=2 refuses the MFD_EXEC opt-out. /\n+\t\tif (errno == EACCES)\n+\t\t\tksft_exit_skip(\"vm.memfd_noexec forbids MFD_EXEC\\n\");\n+\t\tfail_exit(\"memfd_create for execute-mode test\");\n+\t}\n+\n+\tif (fchmod(mfd, 0700) \u003c 0)\n+\t\tfail_exit(\"fchmod for execute-mode test\");\n+\tif (fcntl(mfd, F_ADD_SEALS, F_SEAL_EXEC) \u003c 0)\n+\t\tfail_exit(\"F_ADD_SEALS for execute-mode test\");\n+\n+\t/ The execute bits pull in the write seals: record the whole set. /\n+\tseals = fcntl(mfd, F_GET_SEALS);\n+\tif (seals \u003c 0)\n+\t\tfail_exit(\"F_GET_SEALS for execute-mode test\");\n+\tif (seals != F_WX_SEALS)\n+\t\tksft_exit_fail_msg(\"execute-mode seals 0x%x != 0x%x\\n\", seals,\n+\t\t\t\t F_WX_SEALS);\n+\tksft_print_msg(\"[STAGE 1] exec-mode memfd: execute mask 0100, seals 0x%x\\n\",\n+\t\t seals);\n+\n+\targ.fd = mfd;\n+\tif (ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, \u0026arg) \u003c 0)\n+\t\tfail_exit(\"preserve execute-mode memfd\");\n+\n+\tclose(mfd);\n+}\n+\n+static void restore_and_verify_exec_memfd(int session_fd)\n+{\n+\tstruct liveupdate_session_retrieve_fd arg = {\n+\t\t.size = sizeof(arg),\n+\t\t.token = TEST_EXEC_MEMFD_TOKEN,\n+\t};\n+\tstruct stat st;\n+\tint mfd, seals;\n+\n+\tif (ioctl(session_fd, LIVEUPDATE_SESSION_RETRIEVE_FD, \u0026arg) \u003c 0)\n+\t\tfail_exit(\"retrieve execute-mode memfd\");\n+\tmfd = arg.fd;\n+\n+\tif (fstat(mfd, \u0026st) \u003c 0)\n+\t\tfail_exit(\"fstat execute-mode memfd\");\n+\tif ((st.st_mode \u0026 0111) != 0100)\n+\t\tksft_exit_fail_msg(\"execute mask changed across kexec: 0%o != 0100\\n\",\n+\t\t\t\t st.st_mode \u0026 0111);\n+\n+\tseals = fcntl(mfd, F_GET_SEALS);\n+\tif (seals \u003c 0)\n+\t\tfail_exit(\"F_GET_SEALS for execute-mode test\");\n+\tif (seals != F_WX_SEALS)\n+\t\tksft_exit_fail_msg(\"seals changed across kexec: 0x%x != 0x%x\\n\",\n+\t\t\t\t seals, F_WX_SEALS);\n+\n+\tksft_print_msg(\"[STAGE 2] exec-mode memfd: execute mask 0%o, seals 0x%x\\n\",\n+\t\t st.st_mode \u0026 0111, seals);\n+\n+\tclose(mfd);\n+}\n+\n+/\n+ * The originally reported case: a memfd without execute bits and with\n+ * F_SEAL_EXEC (what memfd_create(MFD_NOEXEC_SEAL) and vm.memfd_noexec=2\n+ * produce) has to come back without execute bits, with the same seal set, and\n+ * still writable by its owner -- F_SEAL_EXEC must not drag in the write seals\n+ * for a memfd that has no execute bits.\n+ /\n+static void create_and_preserve_nx_memfd(int session_fd)\n+{\n+\tstruct liveupdate_session_preserve_fd arg = {\n+\t\t.size = sizeof(arg),\n+\t\t.token = TEST_NX_MEMFD_TOKEN,\n+\t};\n+\tstruct stat st;\n+\tint mfd, seals;\n+\n+\tmfd = memfd_create(\"nx-mode-test\", MFD_ALLOW_SEALING \| MFD_NOEXEC_SEAL);\n+\tif (mfd \u003c 0)\n+\t\tfail_exit(\"memfd_create for NX-mode test\");\n+\n+\tif (fstat(mfd, \u0026st) \u003c 0)\n+\t\tfail_exit(\"fstat for NX-mode test\");\n+\tif (st.st_mode \u0026 0111)\n+\t\tksft_exit_fail_msg(\"NX-mode memfd has execute bits (0%o)\\n\",\n+\t\t\t\t st.st_mode);\n+\n+\tseals = fcntl(mfd, F_GET_SEALS);\n+\tif (seals \u003c 0)\n+\t\tfail_exit(\"F_GET_SEALS for NX-mode test\");\n+\tif (seals != F_SEAL_EXEC)\n+\t\tksft_exit_fail_msg(\"NX-mode seals 0x%x != 0x%x\\n\", seals,\n+\t\t\t\t F_SEAL_EXEC);\n+\n+\tif (pwrite(mfd, TEST_MEMFD_DATA, sizeof(TEST_MEMFD_DATA) - 1, 0) !=\n+\t sizeof(TEST_MEMFD_DATA) - 1)\n+\t\tfail_exit(\"NX-mode memfd is not writable\");\n+\n+\tksft_print_msg(\"[STAGE 1] NX-mode memfd: execute mask 0000, seals 0x%x\\n\",\n+\t\t seals);\n+\n+\targ.fd = mfd;\n+\tif (ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, \u0026arg) \u003c 0)\n+\t\tfail_exit(\"preserve NX-mode memfd\");\n+\n+\tclose(mfd);\n+}\n+\n+static void restore_and_verify_nx_memfd(int session_fd)\n+{\n+\tstruct liveupdate_session_retrieve_fd arg = {\n+\t\t.size = sizeof(arg),\n+\t\t.token = TEST_NX_MEMFD_TOKEN,\n+\t};\n+\tchar buf[sizeof(TEST_MEMFD_DATA)] = {0};\n+\tstruct stat st;\n+\tint mfd, seals;\n+\n+\tif (ioctl(session_fd, LIVEUPDATE_SESSION_RETRIEVE_FD, \u0026arg) \u003c 0)\n+\t\tfail_exit(\"retrieve NX-mode memfd\");\n+\tmfd = arg.fd;\n+\n+\tif (fstat(mfd, \u0026st) \u003c 0)\n+\t\tfail_exit(\"fstat NX-mode memfd\");\n+\tif (st.st_mode \u0026 0111)\n+\t\tksft_exit_fail_msg(\"NX memfd came back executable: execute mask 0%o\\n\",\n+\t\t\t\t st.st_mode \u0026 0111);\n+\n+\tseals = fcntl(mfd, F_GET_SEALS);\n+\tif (seals \u003c 0)\n+\t\tfail_exit(\"F_GET_SEALS for NX-mode test\");\n+\tif (seals != F_SEAL_EXEC)\n+\t\tksft_exit_fail_msg(\"NX memfd seals 0x%x != 0x%x\\n\", seals,\n+\t\t\t\t F_SEAL_EXEC);\n+\n+\tif (pread(mfd, buf, sizeof(buf) - 1, 0) != sizeof(buf) - 1)\n+\t\tfail_exit(\"pread NX-mode memfd\");\n+\tif (strcmp(buf, TEST_MEMFD_DATA))\n+\t\tksft_exit_fail_msg(\"NX memfd data changed: %s\\n\", buf);\n+\n+\tif (pwrite(mfd, \"x\", 1, 0) != 1)\n+\t\tksft_exit_fail_msg(\"NX memfd is not writable by its owner\\n\");\n+\n+\tksft_print_msg(\"[STAGE 2] NX-mode memfd: execute mask 0000, seals 0x%x, writable\\n\",\n+\t\t seals);\n+\n+\tclose(mfd);\n+}\n+\n / Stage 1: Executed before the kexec reboot. */\n static void run_stage_1(int luo_fd)\n {\n@@ -40,6 +236,12 @@ static void run_stage_1(int luo_fd)\n \t\t\t TEST_MEMFD_TOKEN);\n \t}\n \n+\tksft_print_msg(\"[STAGE 1] Preserving mode 0700 + F_SEAL_EXEC memfd...\\n\");\n+\tcreate_and_preserve_exec_memfd(session_fd);\n+\n+\tksft_print_msg(\"[STAGE 1] Preserving NX (no execute bits) + F_SEAL_EXEC memfd...\\n\");\n+\tcreate_and_preserve_nx_memfd(session_fd);\n+\n \tclose(luo_fd);\n \tdaemonize_and_wait();\n }\n@@ -68,6 +270,12 @@ static void run_stage_2(int luo_fd, int state_session_fd)\n \t\tfail_exit(\"restore_and_verify_memfd for token %#x\", TEST_MEMFD_TOKEN);\n \tclose(mfd);\n \n+\tksft_print_msg(\"[STAGE 2] Verifying exact execute-mode round trip...\\n\");\n+\trestore_and_verify_exec_memfd(session_fd);\n+\n+\tksft_print_msg(\"[STAGE 2] Verifying NX round trip...\\n\");\n+\trestore_and_verify_nx_memfd(session_fd);\n+\n \tksft_print_msg(\"[STAGE 2] Test data verified successfully.\\n\");\n \tksft_print_msg(\"[STAGE 2] Finalizing test session...\\n\");\n \tif (luo_session_finish(session_fd) \u003c 0)\n" }
2/1	2026/10/14 08:43	agent	patch-evaluator	4m Model: core Args: null Results: { "EnableConfigs": [ "LIVEUPDATE_MEMFD", "LIVEUPDATE", "KEXEC_HANDOVER", "KEXEC_HANDOVER_ENABLE_DEFAULT", "TMPFS_POSIX_ACL", "MEMFD_CREATE", "TMPFS" ], "FocusSymbols": [ "memfd_luo_preserve", "memfd_luo_freeze", "memfd_luo_unfreeze", "memfd_luo_retrieve", "memfd_luo_finish", "memfd_luo_can_preserve", "memfd_add_seals", "shmem_set_acl" ], "Reasoning": "The patch modifies the Live Update Orchestrator (LUO) support for memfd and shmem/tmpfs. It introduces logic to preserve user/group/other execute permission bits and seal state across kexec live update transitions. It adds seal state freezing checks in memfd_add_seals() and shmem_setattr(), introduces shmem_set_acl() to prevent ACL modifications from diverging execution permissions after snapshotting, and implements unfreeze/error rollback handling in memfd_luo.c. These changes touch reachable core memory management and file system logic accessible from userspace.", "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 b3d3d95b3632992db943db5e3203c4584c36d58d Author: syz-cluster <triage@syzkaller.com> Date: Wed Oct 14 08:43:46 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h index 08b10fea2afc8..f773dd95401d2 100644 --- a/include/linux/kho/abi/memfd.h +++ b/include/linux/kho/abi/memfd.h @@ -87,7 +87,29 @@ struct memfd_luo_ser { struct kho_vmalloc folios; } __packed; +/* + * The execute permission bits are packed in user/group/other order. A record + * with none of these flags set is restored without execute permissions, which + * is also the safe interpretation for records written before these flags + * existed. + / +#define MEMFD_LUO_FL_EXEC_USR BIT(0) +#define MEMFD_LUO_FL_EXEC_GRP BIT(1) +#define MEMFD_LUO_FL_EXEC_OTH BIT(2) +#define MEMFD_LUO_FL_EXEC_MASK (MEMFD_LUO_FL_EXEC_USR \| \ + MEMFD_LUO_FL_EXEC_GRP \| \ + MEMFD_LUO_FL_EXEC_OTH) +#define MEMFD_LUO_ALL_FLAGS MEMFD_LUO_FL_EXEC_MASK + / The compatibility string for memfd file handler / -#define MEMFD_LUO_FH_COMPATIBLE "memfd-v2" +#define MEMFD_LUO_FH_COMPATIBLE "memfd-v3" +/ + * Records written before the execute-bit flags existed. They carry no flag + * bits and are restored without execute permissions: the flags cannot tell + * "the execute bits were clear" and "the writer did not know about the flags" + * apart, and restoring without them is the safe reading. The current kernel + * still accepts these records but never writes them. + / +#define MEMFD_LUO_FH_COMPATIBLE_V2 "memfd-v2" #endif / _LINUX_KHO_ABI_MEMFD_H / diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index e729b9b0e38d4..40e1ce87c30e0 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -32,6 +32,12 @@ struct swap_iocb; isn't directly visible to userspace. / #define SHMEM_F_MAPPING_FROZEN BIT(2) +/ + * Disallow changes to the seal set and execute bits captured by the final LUO + * snapshot. This is set only for the reboot transition and is cleared if the + * transition is rolled back. + / +#define SHMEM_F_SEAL_STATE_FROZEN BIT(3) struct shmem_inode_info { spinlock_t lock; @@ -208,6 +214,20 @@ static inline void shmem_freeze(struct inode inode, bool freeze) SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN; } +/* Must be called with inode lock taken exclusive. / +static inline void shmem_freeze_seal_state(struct inode inode, bool freeze) +{ + if (freeze) + SHMEM_I(inode)->flags \|= SHMEM_F_SEAL_STATE_FROZEN; + else + SHMEM_I(inode)->flags &= ~SHMEM_F_SEAL_STATE_FROZEN; +} + +static inline bool shmem_seal_state_frozen(struct inode inode) +{ + return SHMEM_I(inode)->flags & SHMEM_F_SEAL_STATE_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/memfd.c b/mm/memfd.c index abe13b291ddc8..578ac31ed1a9e 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -278,6 +278,12 @@ int memfd_add_seals(struct file file, unsigned int seals) goto unlock; } + / LUO has taken its final snapshot; do not let the seal set diverge. / + if (shmem_file(file) && shmem_seal_state_frozen(inode)) { + error = -EPERM; + goto unlock; + } + if (file_seals & F_SEAL_SEAL) { error = -EPERM; goto unlock; diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c index 59de210bee5f9..f1f07d90f73d1 100644 --- a/mm/memfd_luo.c +++ b/mm/memfd_luo.c @@ -50,6 +50,16 @@ * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property * is maintained. * + * Execute Permission Bits + * The user, group, and other execute bits are preserved individually. This + * is required to faithfully restore the state protected by ``F_SEAL_EXEC``. + * + * .. note:: + * A record written by an older kernel (``memfd-v2``) does not carry the + * execute bits. It is restored without execute permissions, which is the + * safe reading: an executable memfd preserved by such a kernel comes back + * non-executable, and the next update records the exact state. + * * Seals * File seals set on the memfd are preserved and re-applied on restore. * Only seals known to this LUO version (see ``MEMFD_LUO_ALL_SEALS``) may @@ -84,6 +94,35 @@ #include "internal.h" +static void memfd_luo_record_exec_mode(struct memfd_luo_ser ser, umode_t mode) +{ + u32 flags = 0; + + if (mode & 0100) + flags \|= MEMFD_LUO_FL_EXEC_USR; + if (mode & 0010) + flags \|= MEMFD_LUO_FL_EXEC_GRP; + if (mode & 0001) + flags \|= MEMFD_LUO_FL_EXEC_OTH; + + ser->flags &= ~MEMFD_LUO_FL_EXEC_MASK; + ser->flags \|= flags; +} + +static umode_t memfd_luo_restore_exec_mode(u32 flags) +{ + umode_t mode = 0; + + if (flags & MEMFD_LUO_FL_EXEC_USR) + mode \|= 0100; + if (flags & MEMFD_LUO_FL_EXEC_GRP) + mode \|= 0010; + if (flags & MEMFD_LUO_FL_EXEC_OTH) + mode \|= 0001; + + return mode; +} + static int memfd_luo_preserve_folios(struct file file, struct kho_vmalloc kho_vmalloc, struct memfd_luo_folio_ser out_folios_ser, @@ -300,6 +339,14 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args args) ser->size = inode_size; ser->seals = seals; + /* + * F_SEAL_EXEC freezes each execute permission bit independently, so + * preserve the complete user/group/other execute mask. A record with no + * execute flags is restored without execute permissions, which is also + * the safe interpretation for records written before these flags existed. + / + memfd_luo_record_exec_mode(ser, inode->i_mode); + err = memfd_luo_preserve_folios(args->file, &ser->folios, &folios_ser, &nr_folios); if (err) @@ -323,7 +370,9 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args args) static int memfd_luo_freeze(struct liveupdate_file_op_args args) { + struct inode inode = file_inode(args->file); struct memfd_luo_ser ser; + int seals; if (WARN_ON_ONCE(!args->serialized_data)) return -EINVAL; @@ -331,14 +380,47 @@ static int memfd_luo_freeze(struct liveupdate_file_op_args args) ser = phys_to_virt(args->serialized_data); /* - * The pos might have changed since prepare. Everything else stays the - * same. + * The file is still usable between preserve() and freeze(), so its mode + * and seals can differ from the values recorded by preserve(). Take the + * final snapshot under the inode lock shared with memfd_add_seals(), + * shmem_setattr(), and shmem_set_acl(), then freeze those state fields + * before dropping the lock. This closes the window in which a later + * chmod(), ACL update, or F_ADD_SEALS could otherwise diverge from the + * state handed to the next kernel. / + inode_lock(inode); + + seals = memfd_get_seals(args->file); + if (seals < 0) { + inode_unlock(inode); + return seals; + } + + / The file must not have gained seals that this version does not know. / + if (seals & ~MEMFD_LUO_ALL_SEALS) { + inode_unlock(inode); + return -EOPNOTSUPP; + } + + memfd_luo_record_exec_mode(ser, inode->i_mode); + ser->seals = seals; ser->pos = args->file->f_pos; + shmem_freeze_seal_state(inode, true); + + inode_unlock(inode); return 0; } +static void memfd_luo_unfreeze(struct liveupdate_file_op_args args) +{ + struct inode inode = file_inode(args->file); + + inode_lock(inode); + shmem_freeze_seal_state(inode, false); + inode_unlock(inode); +} + static void memfd_luo_unpreserve(struct liveupdate_file_op_args args) { struct inode inode = file_inode(args->file); @@ -348,6 +430,7 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args args) return; inode_lock(inode); + shmem_freeze_seal_state(inode, false); shmem_freeze(inode, false); ser = phys_to_virt(args->serialized_data); @@ -384,9 +467,31 @@ static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser folios_se } } -static void memfd_luo_finish(struct liveupdate_file_op_args args) +/* + * Release a preserved record: return its folios to the page allocator and free + * the record itself. Only valid for records whose folios were never handed to + * a file -- handing a folio to a file consumes its last reference, and + * memfd_luo_discard_folios() would release it a second time. + / +static void memfd_luo_release_ser(struct memfd_luo_ser ser) { struct memfd_luo_folio_ser folios_ser; + + if (ser->nr_folios) { + folios_ser = kho_restore_vmalloc(&ser->folios); + if (!folios_ser) + goto out; + + memfd_luo_discard_folios(folios_ser, ser->nr_folios); + vfree(folios_ser); + } + +out: + kho_restore_free(ser); +} + +static void memfd_luo_finish(struct liveupdate_file_op_args args) +{ struct memfd_luo_ser ser; / @@ -401,17 +506,7 @@ static void memfd_luo_finish(struct liveupdate_file_op_args args) if (!ser) return; - if (ser->nr_folios) { - folios_ser = kho_restore_vmalloc(&ser->folios); - if (!folios_ser) - goto out; - - memfd_luo_discard_folios(folios_ser, ser->nr_folios); - vfree(folios_ser); - } - -out: - kho_restore_free(ser); + memfd_luo_release_ser(ser); } static int memfd_luo_retrieve_folios(struct file file, @@ -517,32 +612,55 @@ static int memfd_luo_retrieve_folios(struct file file, static int memfd_luo_retrieve(struct liveupdate_file_op_args args) { - struct memfd_luo_folio_ser folios_ser; + struct memfd_luo_folio_ser folios_ser = NULL; struct memfd_luo_ser ser; struct file file; + umode_t exec_mode; int err; ser = phys_to_virt(args->serialized_data); if (!ser) return -EINVAL; - /* Make sure the file only has seals supported by this version. / - if (ser->seals & ~MEMFD_LUO_ALL_SEALS) { + / Make sure the record only contains state supported by this version. / + if ((ser->seals & ~MEMFD_LUO_ALL_SEALS) \|\| + (ser->flags & ~MEMFD_LUO_ALL_FLAGS)) { err = -EOPNOTSUPP; - goto free_ser; + goto release_ser; } / - * The seals are preserved. Allow sealing here so they can be added - * later. + * Restore the folio array before allocating the file. Once this succeeds, + * every later error path can release the preserved folios directly instead + * of allocating memory again while already handling a failure. / + if (ser->nr_folios) { + folios_ser = kho_restore_vmalloc(&ser->folios); + if (!folios_ser) { + / kho_restore_vmalloc() is not safe to retry after failure. / + err = -EINVAL; + goto free_ser; + } + } + file = memfd_alloc_file("", MFD_ALLOW_SEALING); if (IS_ERR(file)) { pr_err("failed to setup file: %pe\n", file); err = PTR_ERR(file); - goto free_ser; + goto discard_folios; } + / + * Reproduce the exact execute mask before the seals are re-applied: + * F_SEAL_EXEC freezes each execute bit, and the W^X rule in + * memfd_add_seals() looks at the mode when deciding whether to imply the + * write seals. The fresh anonymous inode has not been published, so no + * other thread can observe this intermediate state. + / + exec_mode = memfd_luo_restore_exec_mode(ser->flags); + file->f_inode->i_mode &= ~0111; + file->f_inode->i_mode \|= exec_mode; + err = memfd_add_seals(file, ser->seals); if (err) { pr_err("failed to add seals: %pe\n", ERR_PTR(err)); @@ -552,15 +670,12 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args args) vfs_setpos(file, ser->pos, MAX_LFS_FILESIZE); i_size_write(file_inode(file), ser->size); - if (ser->nr_folios) { - folios_ser = kho_restore_vmalloc(&ser->folios); - if (!folios_ser) { - err = -EINVAL; - goto put_file; - } - - err = memfd_luo_retrieve_folios(file, folios_ser, ser->nr_folios); + if (folios_ser) { + /* retrieve_folios() consumes every preserved data folio. / + err = memfd_luo_retrieve_folios(file, folios_ser, + ser->nr_folios); vfree(folios_ser); + folios_ser = NULL; if (err) goto put_file; } @@ -572,9 +687,18 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args args) put_file: fput(file); +discard_folios: + if (folios_ser) { + memfd_luo_discard_folios(folios_ser, ser->nr_folios); + vfree(folios_ser); + } free_ser: kho_restore_free(ser); return err; + +release_ser: + memfd_luo_release_ser(ser); + return err; } static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler, @@ -582,7 +706,12 @@ static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler, { struct inode inode = file_inode(file); - return shmem_file(file) && !inode->i_nlink; + / + * shmem_kernel_file_setup() marks kernel-private files S_PRIVATE. In + * particular, SysV SHM updates SHMEM_I(inode)->flags under its IPC lock, + * which does not serialize with the inode lock used by LUO. + / + return shmem_file(file) && !IS_PRIVATE(inode) && !inode->i_nlink; } static unsigned long memfd_luo_get_id(struct file file) @@ -592,6 +721,7 @@ static unsigned long memfd_luo_get_id(struct file file) static const struct liveupdate_file_ops memfd_luo_file_ops = { .freeze = memfd_luo_freeze, + .unfreeze = memfd_luo_unfreeze, .finish = memfd_luo_finish, .retrieve = memfd_luo_retrieve, .preserve = memfd_luo_preserve, @@ -606,15 +736,62 @@ static struct liveupdate_file_handler memfd_luo_handler = { .compatible = MEMFD_LUO_FH_COMPATIBLE, }; +/ + * Reads records written before the execute-bit flags existed. Those have no + * flag bits and are restored without execute permissions (see the note on + * old records in the DOC section above). can_preserve() never claims a file, + * so an outgoing preservation is always written by the handler above and + * never as "memfd-v2". + / +static bool memfd_luo_can_preserve_v2(struct liveupdate_file_handler handler, + struct file file) +{ + return false; +} + +static const struct liveupdate_file_ops memfd_luo_file_ops_v2 = { + .freeze = memfd_luo_freeze, + .unfreeze = memfd_luo_unfreeze, + .finish = memfd_luo_finish, + .retrieve = memfd_luo_retrieve, + .preserve = memfd_luo_preserve, + .unpreserve = memfd_luo_unpreserve, + .can_preserve = memfd_luo_can_preserve_v2, + .get_id = memfd_luo_get_id, + .owner = THIS_MODULE, +}; + +static struct liveupdate_file_handler memfd_luo_handler_v2 = { + .ops = &memfd_luo_file_ops_v2, + .compatible = MEMFD_LUO_FH_COMPATIBLE_V2, +}; + static int __init memfd_luo_init(void) { - int err = liveupdate_register_file_handler(&memfd_luo_handler); + int err; + + err = liveupdate_register_file_handler(&memfd_luo_handler); + if (err) { + if (err != -EOPNOTSUPP) { + pr_err("Could not register luo filesystem handler: %pe\n", + ERR_PTR(err)); + return err; + } - if (err && err != -EOPNOTSUPP) { - pr_err("Could not register luo filesystem handler: %pe\n", - ERR_PTR(err)); + return 0; + } + + err = liveupdate_register_file_handler(&memfd_luo_handler_v2); + if (err) { + liveupdate_unregister_file_handler(&memfd_luo_handler); - return err; + if (err != -EOPNOTSUPP) { + pr_err("Could not register the memfd-v2 record reader: %pe\n", + ERR_PTR(err)); + return err; + } + + return 0; } return 0; diff --git a/mm/shmem.c b/mm/shmem.c index b51f83c970bb3..55f4dbd429eb9 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1326,11 +1326,10 @@ static int shmem_setattr(struct mnt_idmap idmap, if (error) return error; - if ((info->seals & F_SEAL_EXEC) && (attr->ia_valid & ATTR_MODE)) { - if ((inode->i_mode ^ attr->ia_mode) & 0111) { - return -EPERM; - } - } + if ((attr->ia_valid & ATTR_MODE) && + ((info->seals & F_SEAL_EXEC) \|\| shmem_seal_state_frozen(inode)) && + ((inode->i_mode ^ attr->ia_mode) & 0111)) + return -EPERM; if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) { loff_t oldsize = inode->i_size; @@ -1394,6 +1393,24 @@ static int shmem_setattr(struct mnt_idmap idmap, return error; } +#ifdef CONFIG_TMPFS_POSIX_ACL +static int shmem_set_acl(struct mnt_idmap idmap, struct dentry dentry, + struct posix_acl acl, int type) +{ + struct inode inode = d_inode(dentry); + + / + * An access ACL can rewrite the inode's execute bits without going + * through shmem_setattr(). Once LUO has captured its final seal/mode + * snapshot, reject that alternate mutation path as well. + / + if (type == ACL_TYPE_ACCESS && shmem_seal_state_frozen(inode)) + return -EPERM; + + return simple_set_acl(idmap, dentry, acl, type); +} +#endif + static void shmem_evict_inode(struct inode inode) { struct shmem_inode_info info = SHMEM_I(inode); @@ -5156,7 +5173,9 @@ static const struct inode_operations shmem_inode_operations = { .setattr = shmem_setattr, #ifdef CONFIG_TMPFS_XATTR .listxattr = shmem_listxattr, - .set_acl = simple_set_acl, +#ifdef CONFIG_TMPFS_POSIX_ACL + .set_acl = shmem_set_acl, +#endif .fileattr_get = shmem_fileattr_get, .fileattr_set = shmem_fileattr_set, #endif @@ -5184,7 +5203,7 @@ static const struct inode_operations shmem_dir_inode_operations = { #endif #ifdef CONFIG_TMPFS_POSIX_ACL .setattr = shmem_setattr, - .set_acl = simple_set_acl, + .set_acl = shmem_set_acl, #endif }; @@ -5195,7 +5214,7 @@ static const struct inode_operations shmem_special_inode_operations = { #endif #ifdef CONFIG_TMPFS_POSIX_ACL .setattr = shmem_setattr, - .set_acl = simple_set_acl, + .set_acl = shmem_set_acl, #endif }; diff --git a/tools/testing/selftests/liveupdate/luo_kexec_simple.c b/tools/testing/selftests/liveupdate/luo_kexec_simple.c index d7ac1f3dc4cbc..30836043f894e 100644 --- a/tools/testing/selftests/liveupdate/luo_kexec_simple.c +++ b/tools/testing/selftests/liveupdate/luo_kexec_simple.c @@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0-only +#define _GNU_SOURCE / * Copyright (c) 2025, Google LLC. @@ -8,16 +9,211 @@ * across a single kexec reboot. / +#include <fcntl.h> +#include <sys/ioctl.h> +#include <sys/mman.h> +#include <sys/stat.h> +#include <unistd.h> + +#include <linux/memfd.h> + #include "luo_test_utils.h" +#ifndef F_SEAL_SHRINK +#define F_SEAL_SHRINK 0x0002 +#endif +#ifndef F_SEAL_GROW +#define F_SEAL_GROW 0x0004 +#endif +#ifndef F_SEAL_WRITE +#define F_SEAL_WRITE 0x0008 +#endif +#ifndef F_SEAL_FUTURE_WRITE +#define F_SEAL_FUTURE_WRITE 0x0010 +#endif +#ifndef F_SEAL_EXEC +#define F_SEAL_EXEC 0x0020 +#endif +#ifndef MFD_NOEXEC_SEAL +#define MFD_NOEXEC_SEAL 0x0008U +#endif + +/ + * F_SEAL_EXEC implies the write seals when the memfd has execute bits (the + * W^X rule in memfd_add_seals()), so a memfd that was chmod()ed to 0700 + * before F_SEAL_EXEC was added ends up with exactly this seal set. + / +#define F_WX_SEALS (F_SEAL_EXEC \| F_SEAL_SHRINK \| F_SEAL_GROW \| \ + F_SEAL_WRITE \| F_SEAL_FUTURE_WRITE) + #define TEST_SESSION_NAME "test-session" #define TEST_MEMFD_TOKEN 0x1A +#define TEST_EXEC_MEMFD_TOKEN 0x1B +#define TEST_NX_MEMFD_TOKEN 0x1C #define TEST_MEMFD_DATA "hello kexec world" / Constants for the state-tracking mechanism, specific to this test file. / #define STATE_SESSION_NAME "kexec_simple_state" #define STATE_MEMFD_TOKEN 999 +static void create_and_preserve_exec_memfd(int session_fd) +{ + struct liveupdate_session_preserve_fd arg = { + .size = sizeof(arg), + .token = TEST_EXEC_MEMFD_TOKEN, + }; + int mfd, seals; + + mfd = memfd_create("exec-mode-test", MFD_ALLOW_SEALING \| MFD_EXEC); + if (mfd < 0) { + / vm.memfd_noexec=2 refuses the MFD_EXEC opt-out. / + if (errno == EACCES) + ksft_exit_skip("vm.memfd_noexec forbids MFD_EXEC\n"); + fail_exit("memfd_create for execute-mode test"); + } + + if (fchmod(mfd, 0700) < 0) + fail_exit("fchmod for execute-mode test"); + if (fcntl(mfd, F_ADD_SEALS, F_SEAL_EXEC) < 0) + fail_exit("F_ADD_SEALS for execute-mode test"); + + / The execute bits pull in the write seals: record the whole set. / + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for execute-mode test"); + if (seals != F_WX_SEALS) + ksft_exit_fail_msg("execute-mode seals 0x%x != 0x%x\n", seals, + F_WX_SEALS); + ksft_print_msg("[STAGE 1] exec-mode memfd: execute mask 0100, seals 0x%x\n", + seals); + + arg.fd = mfd; + if (ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, &arg) < 0) + fail_exit("preserve execute-mode memfd"); + + close(mfd); +} + +static void restore_and_verify_exec_memfd(int session_fd) +{ + struct liveupdate_session_retrieve_fd arg = { + .size = sizeof(arg), + .token = TEST_EXEC_MEMFD_TOKEN, + }; + struct stat st; + int mfd, seals; + + if (ioctl(session_fd, LIVEUPDATE_SESSION_RETRIEVE_FD, &arg) < 0) + fail_exit("retrieve execute-mode memfd"); + mfd = arg.fd; + + if (fstat(mfd, &st) < 0) + fail_exit("fstat execute-mode memfd"); + if ((st.st_mode & 0111) != 0100) + ksft_exit_fail_msg("execute mask changed across kexec: 0%o != 0100\n", + st.st_mode & 0111); + + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for execute-mode test"); + if (seals != F_WX_SEALS) + ksft_exit_fail_msg("seals changed across kexec: 0x%x != 0x%x\n", + seals, F_WX_SEALS); + + ksft_print_msg("[STAGE 2] exec-mode memfd: execute mask 0%o, seals 0x%x\n", + st.st_mode & 0111, seals); + + close(mfd); +} + +/ + * The originally reported case: a memfd without execute bits and with + * F_SEAL_EXEC (what memfd_create(MFD_NOEXEC_SEAL) and vm.memfd_noexec=2 + * produce) has to come back without execute bits, with the same seal set, and + * still writable by its owner -- F_SEAL_EXEC must not drag in the write seals + * for a memfd that has no execute bits. + / +static void create_and_preserve_nx_memfd(int session_fd) +{ + struct liveupdate_session_preserve_fd arg = { + .size = sizeof(arg), + .token = TEST_NX_MEMFD_TOKEN, + }; + struct stat st; + int mfd, seals; + + mfd = memfd_create("nx-mode-test", MFD_ALLOW_SEALING \| MFD_NOEXEC_SEAL); + if (mfd < 0) + fail_exit("memfd_create for NX-mode test"); + + if (fstat(mfd, &st) < 0) + fail_exit("fstat for NX-mode test"); + if (st.st_mode & 0111) + ksft_exit_fail_msg("NX-mode memfd has execute bits (0%o)\n", + st.st_mode); + + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for NX-mode test"); + if (seals != F_SEAL_EXEC) + ksft_exit_fail_msg("NX-mode seals 0x%x != 0x%x\n", seals, + F_SEAL_EXEC); + + if (pwrite(mfd, TEST_MEMFD_DATA, sizeof(TEST_MEMFD_DATA) - 1, 0) != + sizeof(TEST_MEMFD_DATA) - 1) + fail_exit("NX-mode memfd is not writable"); + + ksft_print_msg("[STAGE 1] NX-mode memfd: execute mask 0000, seals 0x%x\n", + seals); + + arg.fd = mfd; + if (ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, &arg) < 0) + fail_exit("preserve NX-mode memfd"); + + close(mfd); +} + +static void restore_and_verify_nx_memfd(int session_fd) +{ + struct liveupdate_session_retrieve_fd arg = { + .size = sizeof(arg), + .token = TEST_NX_MEMFD_TOKEN, + }; + char buf[sizeof(TEST_MEMFD_DATA)] = {0}; + struct stat st; + int mfd, seals; + + if (ioctl(session_fd, LIVEUPDATE_SESSION_RETRIEVE_FD, &arg) < 0) + fail_exit("retrieve NX-mode memfd"); + mfd = arg.fd; + + if (fstat(mfd, &st) < 0) + fail_exit("fstat NX-mode memfd"); + if (st.st_mode & 0111) + ksft_exit_fail_msg("NX memfd came back executable: execute mask 0%o\n", + st.st_mode & 0111); + + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for NX-mode test"); + if (seals != F_SEAL_EXEC) + ksft_exit_fail_msg("NX memfd seals 0x%x != 0x%x\n", seals, + F_SEAL_EXEC); + + if (pread(mfd, buf, sizeof(buf) - 1, 0) != sizeof(buf) - 1) + fail_exit("pread NX-mode memfd"); + if (strcmp(buf, TEST_MEMFD_DATA)) + ksft_exit_fail_msg("NX memfd data changed: %s\n", buf); + + if (pwrite(mfd, "x", 1, 0) != 1) + ksft_exit_fail_msg("NX memfd is not writable by its owner\n"); + + ksft_print_msg("[STAGE 2] NX-mode memfd: execute mask 0000, seals 0x%x, writable\n", + seals); + + close(mfd); +} + / Stage 1: Executed before the kexec reboot. */ static void run_stage_1(int luo_fd) { @@ -40,6 +236,12 @@ static void run_stage_1(int luo_fd) TEST_MEMFD_TOKEN); } + ksft_print_msg("[STAGE 1] Preserving mode 0700 + F_SEAL_EXEC memfd...\n"); + create_and_preserve_exec_memfd(session_fd); + + ksft_print_msg("[STAGE 1] Preserving NX (no execute bits) + F_SEAL_EXEC memfd...\n"); + create_and_preserve_nx_memfd(session_fd); + close(luo_fd); daemonize_and_wait(); } @@ -68,6 +270,12 @@ static void run_stage_2(int luo_fd, int state_session_fd) fail_exit("restore_and_verify_memfd for token %#x", TEST_MEMFD_TOKEN); close(mfd); + ksft_print_msg("[STAGE 2] Verifying exact execute-mode round trip...\n"); + restore_and_verify_exec_memfd(session_fd); + + ksft_print_msg("[STAGE 2] Verifying NX round trip...\n"); + restore_and_verify_nx_memfd(session_fd); + ksft_print_msg("[STAGE 2] Test data verified successfully.\n"); ksft_print_msg("[STAGE 2] Finalizing test session...\n"); if (luo_session_finish(session_fd) < 0)
3/2	2026/10/14 08:43	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12901 output: 49 thoughts: 1032 Thoughts: Analyzing the KHO/LIVEUPDATE Memory File Descriptor Patch Okay, let's break this down. First, I need to understand the intent and implications of these changes. My initial thought is this is related to Live Update (LUO) and Kernel Hot-patching (KHO), which I'm familiar with but I need to make sure I grasp the current context. I see new `MEMFD_LUO_FL_EXEC_` flags added in `memfd.h`. These likely control executable permissions when dealing with LUO, and the added compatibility flags for memfd-v3 suggest an evolution of the memfd functionality related to this feature. Good. The modifications to `shmem_fs.h` are crucial. Adding `SHMEM_F_SEAL_STATE_FROZEN` and associated functions (`shmem_freeze_seal_state`, `shmem_seal_state_frozen`) points towards a mechanism for hardening shared memory (shmem) objects, probably memfds specifically, during the Live Update process. The introduction of a "frozen" seal state is a clear indicator. This likely provides a method to establish the snapshot. The changes in `mm/memfd.c` confirms this. We are now preventing seal changes on shmem files when they are frozen: "LUO has taken its final snapshot; do not let the seal set diverge." This locking down of seals is essential for preventing modifications after a LUO snapshot. Now, looking at `mm/memfd_luo.c`, this is where things get interesting. We're recording and restoring execute modes using `memfd_luo_record_exec_mode` and `memfd_luo_restore_exec_mode`, a critical step for preserving state during the LUO lifecycle. `memfd_luo_freeze()` is the pivotal function; it locks the inode, gets the seals, records* the execution mode, and sets the frozen state. The `memfd_luo_preserve` functions are involved too. The `memfd_luo_unfreeze` and `memfd_luo_unpreserve` functions suggest a full life cycle for the snapshots. `memfd_luo_can_preserve()` now checks that the inode is not `IS_PRIVATE`, which makes sense; we don't need to preserve private inodes. The versioning (v2, v3) handlers show this is an evolving feature. The changes in `mm/shmem.c` are protecting the integrity of the frozen inode. The `shmem_setattr()` modification reinforces the execution seal, now including a check for the frozen state; modifications to executable bits are now forbidden. The addition of `shmem_set_acl()` and the `shmem_seal_state_frozen` check are brilliant. This prevents ACLs (Access Control Lists) from bypassing the `shmem_setattr` and manipulating the execute permissions after a LUO snapshot has been taken, and further ensuring that the hardened mode is not circumvented. We want to protect against this potential weakness. Finally, the inclusion of changes in `tools/testing/selftests/liveupdate/...` suggests that this work is thoroughly tested. It's good to see integration with testing infrastructure. So, in summary, this patch is tightly focused on ensuring a safe and reliable live update/kernel hotpatching (KHO) workflow for memfds. It establishes a "frozen" state for shared memory objects, carefully recording and restoring crucial metadata (especially execute permissions) and adding multiple layers of protection against unwanted modification during the update process. I should make sure that this is connected to any documentation regarding the KHO/LUO implementation. I will check for Kconfig options. I need to refresh myself on LUO, KHO, and memfd specifics.
4/2	2026/10/14 08:44	tool	grepper	0m Args: { "Expression": "MEMFD_LUO\|LIVEUPDATE\|KHO", "PathPrefixes": [ "mm/", "include/", "kernel/", "fs/" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 1431 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (37 files in total):\ninclude/linux/kho/abi/block.h:9\ninclude/linux/kho/abi/kexec_handover.h:32\ninclude/linux/kho/abi/kexec_metadata.h:7\ninclude/linux/kho/abi/luo.h:15\ninclude/linux/kho/abi/memblock.h:9\ninclude/linux/kho/abi/memfd.h:20\ninclude/linux/kho_block.h:6\ninclude/linux/kho_radix_tree.h:5\ninclude/linux/liveupdate.h:8\ninclude/linux/memblock.h:4\ninclude/net/devlink.h:4\ninclude/net/nexthop.h:1\ninclude/soc/mscc/ocelot.h:3\ninclude/uapi/linux/bpf.h:1\ninclude/uapi/linux/fib_rules.h:1\ninclude/uapi/linux/liveupdate.h:42\ninclude/uapi/linux/netfilter/xt_addrtype.h:1\ninclude/uapi/linux/nexthop.h:3\ninclude/uapi/linux/rtnetlink.h:1\ninclude/uapi/linux/snmp.h:1\nkernel/kexec_file.c:2\nkernel/liveupdate/Kconfig:8\nkernel/liveupdate/Makefile:1\nkernel/liveupdate/kexec_handover.c:83\nkernel/liveupdate/kexec_handover_debug.c:1\nkernel/liveupdate/kexec_handover_debugfs.c:6\nkernel/liveupdate/kho_block.c:8\nkernel/liveupdate/luo_core.c:12\nkernel/liveupdate/luo_file.c:4\nkernel/liveupdate/luo_flb.c:1\nkernel/liveupdate/luo_internal.h:2\nkernel/liveupdate/luo_session.c:13\nmm/Kconfig:1\nmm/Makefile:1\nmm/memblock.c:28\nmm/memfd_luo.c:19\nmm/mm_init.c:1\n\ninclude/linux/kho/abi/block.h-7-/*\ninclude/linux/kho/abi/block.h:8: DOC: KHO Serialization Blocks ABI\ninclude/linux/kho/abi/block.h-9- \ninclude/linux/kho/abi/block.h:10: Subsystems using the KHO Serialization Blocks framework rely on the stable\ninclude/linux/kho/abi/block.h-11- * Application Binary Interface defined below to pass serialized state from a\n--\ninclude/linux/kho/abi/block.h-16- * structures defined here constitutes a breaking change. Such changes require\ninclude/linux/kho/abi/block.h:17: * incrementing the version number in the `KHO_FDT_COMPATIBLE` string to\ninclude/linux/kho/abi/block.h-18- * prevent a new kernel from misinterpreting data from an old kernel.\n--\ninclude/linux/kho/abi/block.h-24-\ninclude/linux/kho/abi/block.h:25:#ifndef _LINUX_KHO_ABI_BLOCK_H\ninclude/linux/kho/abi/block.h:26:#define _LINUX_KHO_ABI_BLOCK_H\ninclude/linux/kho/abi/block.h-27-\n--\ninclude/linux/kho/abi/block.h-31-/*\ninclude/linux/kho/abi/block.h:32: KHO_BLOCK_SIZE - The size of each serialization block.\ninclude/linux/kho/abi/block.h-33- \ninclude/linux/kho/abi/block.h-34- This is defined as PAGE_SIZE. PAGE_SIZE is ABI compliant because live\ninclude/linux/kho/abi/block.h:35: * update between kernels with different page sizes is not supported by KHO.\ninclude/linux/kho/abi/block.h-36- /\ninclude/linux/kho/abi/block.h:37:#define KHO_BLOCK_SIZE\t\t\tPAGE_SIZE\ninclude/linux/kho/abi/block.h-38-\n--\ninclude/linux/kho/abi/block.h=49=struct kho_block_header_ser {\n--\ninclude/linux/kho/abi/block.h-53-\ninclude/linux/kho/abi/block.h:54:#endif / _LINUX_KHO_ABI_BLOCK_H /\n--\ninclude/linux/kho/abi/kexec_handover.h-9-\ninclude/linux/kho/abi/kexec_handover.h:10:#ifndef _LINUX_KHO_ABI_KEXEC_HANDOVER_H\ninclude/linux/kho/abi/kexec_handover.h:11:#define _LINUX_KHO_ABI_KEXEC_HANDOVER_H\ninclude/linux/kho/abi/kexec_handover.h-12-\n--\ninclude/linux/kho/abi/kexec_handover.h-30- referenced here constitutes a breaking change. Such changes require\ninclude/linux/kho/abi/kexec_handover.h:31: * incrementing the version number in KHO_FDT_COMPATIBLE to prevent a new kernel\ninclude/linux/kho/abi/kexec_handover.h-32- * from misinterpreting data from an older kernel. Changes are allowed provided\n--\ninclude/linux/kho/abi/kexec_handover.h-63- \ninclude/linux/kho/abi/kexec_handover.h:64: Root KHO Node (/):\ninclude/linux/kho/abi/kexec_handover.h-65- * - compatible: \"kho-v3\"\ninclude/linux/kho/abi/kexec_handover.h-66- \ninclude/linux/kho/abi/kexec_handover.h:67: Identifies the overall KHO ABI version.\ninclude/linux/kho/abi/kexec_handover.h-68- \n--\ninclude/linux/kho/abi/kexec_handover.h-76- describe other preserved data blobs. The \u003csubnode-name-N\u003e\ninclude/linux/kho/abi/kexec_handover.h:77: * is provided by the subsystem that uses KHO for preserving its\ninclude/linux/kho/abi/kexec_handover.h-78- * data.\n--\ninclude/linux/kho/abi/kexec_handover.h-91-\ninclude/linux/kho/abi/kexec_handover.h:92:/* The compatible string for the KHO FDT root node. /\ninclude/linux/kho/abi/kexec_handover.h:93:#define KHO_FDT_COMPATIBLE \"kho-v4\"\ninclude/linux/kho/abi/kexec_handover.h-94-\ninclude/linux/kho/abi/kexec_handover.h-95-/ The FDT property for the preserved memory map. /\ninclude/linux/kho/abi/kexec_handover.h:96:#define KHO_FDT_MEMORY_MAP_PROP_NAME \"preserved-memory-map\"\ninclude/linux/kho/abi/kexec_handover.h-97-\ninclude/linux/kho/abi/kexec_handover.h-98-/ The FDT property for preserved data blobs. /\ninclude/linux/kho/abi/kexec_handover.h:99:#define KHO_SUB_TREE_PROP_NAME \"preserved-data\"\ninclude/linux/kho/abi/kexec_handover.h-100-\ninclude/linux/kho/abi/kexec_handover.h-101-/ The FDT property for the size of preserved data blobs. /\ninclude/linux/kho/abi/kexec_handover.h:102:#define KHO_SUB_TREE_SIZE_PROP_NAME \"blob-size\"\ninclude/linux/kho/abi/kexec_handover.h-103-\n--\ninclude/linux/kho/abi/kexec_handover.h-108- a set of structures and helper macros. The layout of these structures is a\ninclude/linux/kho/abi/kexec_handover.h:109: * stable contract between kernels and is versioned by the KHO_FDT_COMPATIBLE\ninclude/linux/kho/abi/kexec_handover.h-110- * string.\n--\ninclude/linux/kho/abi/kexec_handover.h-120-/* Helper macro to define a union for a serializable pointer. /\ninclude/linux/kho/abi/kexec_handover.h:121:#define DECLARE_KHOSER_PTR(name, type)\t\\\ninclude/linux/kho/abi/kexec_handover.h-122-\tunion { \\\n--\ninclude/linux/kho/abi/kexec_handover.h-127-/ Stores the physical address of a serializable pointer. /\ninclude/linux/kho/abi/kexec_handover.h:128:#define KHOSER_STORE_PTR(dest, val) \\\ninclude/linux/kho/abi/kexec_handover.h-129-\t({ \\\n--\ninclude/linux/kho/abi/kexec_handover.h-135-/ Loads the stored physical address back to a pointer. /\ninclude/linux/kho/abi/kexec_handover.h:136:#define KHOSER_LOAD_PTR(src)\t\t\t\t\t\t\\\ninclude/linux/kho/abi/kexec_handover.h-137-\t({ \\\n--\ninclude/linux/kho/abi/kexec_handover.h=147=struct kho_vmalloc_hdr {\ninclude/linux/kho/abi/kexec_handover.h:148:\tDECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk );\ninclude/linux/kho/abi/kexec_handover.h-149-};\ninclude/linux/kho/abi/kexec_handover.h-150-\ninclude/linux/kho/abi/kexec_handover.h:151:#define KHO_VMALLOC_SIZE\t\t\t\t\\\ninclude/linux/kho/abi/kexec_handover.h-152-\t((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \\\n--\ninclude/linux/kho/abi/kexec_handover.h=161=struct kho_vmalloc_chunk {\ninclude/linux/kho/abi/kexec_handover.h-162-\tstruct kho_vmalloc_hdr hdr;\ninclude/linux/kho/abi/kexec_handover.h:163:\tu64 phys[KHO_VMALLOC_SIZE];\ninclude/linux/kho/abi/kexec_handover.h-164-};\n--\ninclude/linux/kho/abi/kexec_handover.h=173=struct kho_vmalloc {\ninclude/linux/kho/abi/kexec_handover.h:174:\tDECLARE_KHOSER_PTR(first, struct kho_vmalloc_chunk );\ninclude/linux/kho/abi/kexec_handover.h-175-\tunsigned int total_pages;\n--\ninclude/linux/kho/abi/kexec_handover.h-180-/\ninclude/linux/kho/abi/kexec_handover.h:181: DOC: KHO persistent memory tracker\ninclude/linux/kho/abi/kexec_handover.h-182- \ninclude/linux/kho/abi/kexec_handover.h:183: KHO tracks preserved memory using a radix tree data structure. Each node of\ninclude/linux/kho/abi/kexec_handover.h-184- * the tree is exactly a single page. The leaf nodes are bitmaps where each set\n--\ninclude/linux/kho/abi/kexec_handover.h-248- \ninclude/linux/kho/abi/kexec_handover.h:249: The data structures defined here are part of the KHO ABI. Any modification\ninclude/linux/kho/abi/kexec_handover.h-250- * to these structures that breaks backward compatibility must be accompanied by\n--\ninclude/linux/kho/abi/kexec_handover.h-255-/\ninclude/linux/kho/abi/kexec_handover.h:256: Defines constants for the KHO radix tree structure, used to track preserved\ninclude/linux/kho/abi/kexec_handover.h-257- * memory. These constants govern the indexing, sizing, and depth of the tree.\n--\ninclude/linux/kho/abi/kexec_handover.h=259=enum kho_radix_consts {\n--\ninclude/linux/kho/abi/kexec_handover.h-263-\t /\ninclude/linux/kho/abi/kexec_handover.h:264:\tKHO_ORDER_0_LOG2 = 64 - PAGE_SHIFT,\ninclude/linux/kho/abi/kexec_handover.h-265-\ninclude/linux/kho/abi/kexec_handover.h-266-\t/ Size of the table in kho_radix_node, in log2 /\ninclude/linux/kho/abi/kexec_handover.h:267:\tKHO_TABLE_SIZE_LOG2 = const_ilog2(PAGE_SIZE / sizeof(phys_addr_t)),\ninclude/linux/kho/abi/kexec_handover.h-268-\ninclude/linux/kho/abi/kexec_handover.h-269-\t/ Number of bits in the kho_radix_leaf bitmap, in log2 /\ninclude/linux/kho/abi/kexec_handover.h:270:\tKHO_BITMAP_SIZE_LOG2 = PAGE_SHIFT + const_ilog2(BITS_PER_BYTE),\ninclude/linux/kho/abi/kexec_handover.h-271-\n--\ninclude/linux/kho/abi/kexec_handover.h-275-\t /\ninclude/linux/kho/abi/kexec_handover.h:276:\tKHO_TREE_MAX_DEPTH =\ninclude/linux/kho/abi/kexec_handover.h:277:\t\tDIV_ROUND_UP(KHO_ORDER_0_LOG2 - KHO_BITMAP_SIZE_LOG2 + 1,\ninclude/linux/kho/abi/kexec_handover.h:278:\t\t\t KHO_TABLE_SIZE_LOG2) + 1,\ninclude/linux/kho/abi/kexec_handover.h-279-};\n--\ninclude/linux/kho/abi/kexec_handover.h=281=struct kho_radix_node {\ninclude/linux/kho/abi/kexec_handover.h:282:\tu64 table[1 \u003c\u003c KHO_TABLE_SIZE_LOG2];\ninclude/linux/kho/abi/kexec_handover.h-283-};\n--\ninclude/linux/kho/abi/kexec_handover.h=285=struct kho_radix_leaf {\ninclude/linux/kho/abi/kexec_handover.h:286:\tDECLARE_BITMAP(bitmap, 1 \u003c\u003c KHO_BITMAP_SIZE_LOG2);\ninclude/linux/kho/abi/kexec_handover.h-287-};\ninclude/linux/kho/abi/kexec_handover.h-288-\ninclude/linux/kho/abi/kexec_handover.h:289:#endif\t/* _LINUX_KHO_ABI_KEXEC_HANDOVER_H /\n--\ninclude/linux/kho/abi/kexec_metadata.h-7- It is registered via kho_add_subtree(), keeping it independent from the core\ninclude/linux/kho/abi/kexec_metadata.h:8: * KHO ABI. This allows the metadata format to evolve without affecting other\ninclude/linux/kho/abi/kexec_metadata.h:9: * KHO consumers.\ninclude/linux/kho/abi/kexec_metadata.h-10- \n--\ninclude/linux/kho/abi/kexec_metadata.h-17-\ninclude/linux/kho/abi/kexec_metadata.h:18:#ifndef _LINUX_KHO_ABI_KEXEC_METADATA_H\ninclude/linux/kho/abi/kexec_metadata.h:19:#define _LINUX_KHO_ABI_KEXEC_METADATA_H\ninclude/linux/kho/abi/kexec_metadata.h-20-\n--\ninclude/linux/kho/abi/kexec_metadata.h-23-\ninclude/linux/kho/abi/kexec_metadata.h:24:#define KHO_KEXEC_METADATA_VERSION 1\ninclude/linux/kho/abi/kexec_metadata.h-25-\n--\ninclude/linux/kho/abi/kexec_metadata.h=38=struct kho_kexec_metadata {\n--\ninclude/linux/kho/abi/kexec_metadata.h-43-\ninclude/linux/kho/abi/kexec_metadata.h:44:#define KHO_METADATA_NODE_NAME \"kexec-metadata\"\ninclude/linux/kho/abi/kexec_metadata.h-45-\ninclude/linux/kho/abi/kexec_metadata.h:46:#endif / _LINUX_KHO_ABI_KEXEC_METADATA_H /\n--\ninclude/linux/kho/abi/luo.h-13- kernel. The ABI is built upon the Kexec HandOver framework and registers\ninclude/linux/kho/abi/luo.h:14: * the central `struct luo_ser` via the KHO raw subtree API.\ninclude/linux/kho/abi/luo.h-15- \n--\ninclude/linux/kho/abi/luo.h-25- \ninclude/linux/kho/abi/luo.h:26: * KHO Structure Overview:\ninclude/linux/kho/abi/luo.h:27: * The entire LUO state is encapsulated within a single KHO entry named \"LUO\".\ninclude/linux/kho/abi/luo.h-28- * This entry contains the `struct luo_ser` structure.\n--\ninclude/linux/kho/abi/luo.h-56-\ninclude/linux/kho/abi/luo.h:57:#ifndef _LINUX_KHO_ABI_LUO_H\ninclude/linux/kho/abi/luo.h:58:#define _LINUX_KHO_ABI_LUO_H\ninclude/linux/kho/abi/luo.h-59-\n--\ninclude/linux/kho/abi/luo.h-64-/\ninclude/linux/kho/abi/luo.h:65: The LUO state is registered under this KHO entry name.\ninclude/linux/kho/abi/luo.h-66- /\ninclude/linux/kho/abi/luo.h:67:#define LUO_KHO_ENTRY_NAME\t\"LUO\"\ninclude/linux/kho/abi/luo.h-68-#define LUO_ABI_COMPATIBLE\t\"luo-v5\"\n--\ninclude/linux/kho/abi/luo.h=80=struct luo_ser {\n--\ninclude/linux/kho/abi/luo.h-86-\ninclude/linux/kho/abi/luo.h:87:#define LIVEUPDATE_HNDL_COMPAT_LENGTH\t48\ninclude/linux/kho/abi/luo.h-88-\n--\ninclude/linux/kho/abi/luo.h=97=struct luo_file_ser {\ninclude/linux/kho/abi/luo.h:98:\tchar compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];\ninclude/linux/kho/abi/luo.h-99-\tu64 data;\n--\ninclude/linux/kho/abi/luo.h=131=struct luo_session_ser {\ninclude/linux/kho/abi/luo.h:132:\tchar name[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/linux/kho/abi/luo.h-133-\tstruct luo_file_set_ser file_set_ser;\n--\ninclude/linux/kho/abi/luo.h-136-/ The max size is set so it can be reliably used during in serialization */\ninclude/linux/kho/abi/luo.h:137:#define LIVEUPDATE_FLB_COMPAT_LENGTH\t48\ninclude/linux/kho/abi/luo.h-138-\n--\ninclude/linux/kho/abi/luo.h=174=struct luo_flb_ser {\ninclude/linux/kho/abi/luo.h:175:\tchar name[LIVEUPDATE_FLB_COMPAT_LENGTH];\ninclude/linux/kho/abi/luo.h-176-\tu64 data;\n--\n\n" }
5/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 19993 output: 33 thoughts: 43 Thoughts: Okay, let's dive into these Kconfig options related to KHO, LIVEUPDATE, and MEMFD_LUO. I need to understand how these features are configured. My initial thought is to check the relevant Kconfig files. Specifically, I should be looking at `kernel/liveupdate/Kconfig` and `mm/Kconfig`. These are the most likely places to find the configuration options that control these kernel features. Let's see what's in there.
6/2	2026/10/14 08:44	tool	read-file	0m Args: { "File": "kernel/liveupdate/Kconfig", "FirstLine": 1, "LineCount": 80 } 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 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" }
7/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21238 output: 34 thoughts: 31 Thoughts: Here's a summary of my thought process, as requested: Digging Deeper into LIVEUPDATE_MEMFD Dependencies Okay, so I've been focusing on `kernel/liveupdate/Kconfig` and `mm/Kconfig` lately, specifically around the `LIVEUPDATE_MEMFD` configuration option. I need to make sure I haven't missed anything critical related to this functionality. My thought is, while I have a good grasp on the initial implementations, a thorough review of these Kconfig files is crucial. I want to ensure I understand every dependency, every potential interaction, and every conditional build scenario involving `LIVEUPDATE_MEMFD`. It's about due diligence at this stage, preventing any oversight or unforeseen consequences down the road. This deep dive should give me a complete picture of its context within the kernel.
8/2	2026/10/14 08:44	tool	read-file	0m Args: { "File": "kernel/liveupdate/Kconfig", "FirstLine": 75, "LineCount": 25 } Results: { "Contents": " 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" }
9/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21665 output: 28 thoughts: 24 Thoughts: Okay, here's my summary, taking the perspective of someone familiar with kernel build processes and memory management, focusing on the specific file: Investigating the Compilation of `mm/memfd_luo.c` Alright, let's dive into this. My immediate thought is, I need to understand how the kernel build system handles `mm/memfd_luo.c`. Knowing how a file gets compiled is critical for understanding its dependencies, build-time configurations, and how it’s ultimately linked into the kernel image. I need to check the `mm/Makefile` – that's the obvious starting point. It's the central hub for build instructions within the `mm` directory. I'm expecting to find rules that define how `memfd_luo.c` is turned into an object file (`.o`), along with any flags or prerequisites involved. I'm looking for things like compiler flags (optimization, debugging, etc.), inclusion of header files, and possibly linker directives if it's handled differently than a standard source file. I’ll also be searching for any conditional compilation based on kernel configuration options, as `memfd_luo.c` probably interacts with other parts of the memory management subsystem. This is where I'll find clues about what features might enable or disable parts of the code. Ultimately, I want to form a mental map of how this specific source file plays its role in the bigger picture of the kernel's memory management.
10/2	2026/10/14 08:44	tool	grepper	0m Args: { "Expression": "memfd_luo", "PathPrefixes": [ "mm/" ] } Results: { "Output": "\nFull output is too long, showing 200 out of 202 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (2 files in total):\nmm/Makefile:1\nmm/memfd_luo.c:71\n\nmm/Makefile=102=obj-$(CONFIG_PAGE_COUNTER) += page_counter.o\nmm/Makefile:103:obj-$(CONFIG_LIVEUPDATE_MEMFD) += memfd_luo.o\nmm/Makefile-104-obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o\n--\nmm/memfd_luo.c-96-\nmm/memfd_luo.c:97:static void memfd_luo_record_exec_mode(struct memfd_luo_ser ser, umode_t mode)\nmm/memfd_luo.c-98-{\n--\nmm/memfd_luo.c-111-\nmm/memfd_luo.c:112:static umode_t memfd_luo_restore_exec_mode(u32 flags)\nmm/memfd_luo.c-113-{\n--\nmm/memfd_luo.c-125-\nmm/memfd_luo.c:126:static int memfd_luo_preserve_folios(struct file file,\nmm/memfd_luo.c-127-\t\t\t\t struct kho_vmalloc kho_vmalloc,\nmm/memfd_luo.c:128:\t\t\t\t struct memfd_luo_folio_ser out_folios_ser,\nmm/memfd_luo.c-129-\t\t\t\t u64 nr_foliosp)\n--\nmm/memfd_luo.c-131-\tstruct inode inode = file_inode(file);\nmm/memfd_luo.c:132:\tstruct memfd_luo_folio_ser folios_ser;\nmm/memfd_luo.c-133-\tunsigned int max_folios;\n--\nmm/memfd_luo.c-187-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:188:\t\tstruct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-189-\t\tstruct folio folio = folios[i];\n--\nmm/memfd_luo.c-269-\nmm/memfd_luo.c:270:static void memfd_luo_unpreserve_folios(struct kho_vmalloc kho_vmalloc,\nmm/memfd_luo.c:271:\t\t\t\t\tstruct memfd_luo_folio_ser folios_ser,\nmm/memfd_luo.c-272-\t\t\t\t\tu64 nr_folios)\n--\nmm/memfd_luo.c-281-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:282:\t\tconst struct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-283-\t\tstruct folio folio;\n--\nmm/memfd_luo.c-296-\nmm/memfd_luo.c:297:static int memfd_luo_preserve(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-298-{\nmm/memfd_luo.c-299-\tstruct inode inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:300:\tstruct memfd_luo_folio_ser folios_ser;\nmm/memfd_luo.c:301:\tstruct memfd_luo_ser ser;\nmm/memfd_luo.c-302-\tu64 nr_folios, inode_size;\n--\nmm/memfd_luo.c-347-\t /\nmm/memfd_luo.c:348:\tmemfd_luo_record_exec_mode(ser, inode-\u003ei_mode);\nmm/memfd_luo.c-349-\nmm/memfd_luo.c:350:\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\nmm/memfd_luo.c-351-\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n--\nmm/memfd_luo.c-370-\nmm/memfd_luo.c:371:static int memfd_luo_freeze(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-372-{\nmm/memfd_luo.c-373-\tstruct inode inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:374:\tstruct memfd_luo_ser ser;\nmm/memfd_luo.c-375-\tint seals;\n--\nmm/memfd_luo.c-404-\nmm/memfd_luo.c:405:\tmemfd_luo_record_exec_mode(ser, inode-\u003ei_mode);\nmm/memfd_luo.c-406-\tser-\u003eseals = seals;\n--\nmm/memfd_luo.c-414-\nmm/memfd_luo.c:415:static void memfd_luo_unfreeze(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-416-{\n--\nmm/memfd_luo.c-423-\nmm/memfd_luo.c:424:static void memfd_luo_unpreserve(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-425-{\nmm/memfd_luo.c-426-\tstruct inode inode = file_inode(args-\u003efile);\nmm/memfd_luo.c:427:\tstruct memfd_luo_ser ser;\nmm/memfd_luo.c-428-\n--\nmm/memfd_luo.c-437-\nmm/memfd_luo.c:438:\tmemfd_luo_unpreserve_folios(\u0026ser-\u003efolios, args-\u003eprivate_data,\nmm/memfd_luo.c-439-\t\t\t\t ser-\u003enr_folios);\n--\nmm/memfd_luo.c-444-\nmm/memfd_luo.c:445:static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser folios_ser,\nmm/memfd_luo.c-446-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-450-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:451:\t\tconst struct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-452-\t\tstruct folio folio;\n--\nmm/memfd_luo.c-473- a file -- handing a folio to a file consumes its last reference, and\nmm/memfd_luo.c:474: * memfd_luo_discard_folios() would release it a second time.\nmm/memfd_luo.c-475- /\nmm/memfd_luo.c:476:static void memfd_luo_release_ser(struct memfd_luo_ser ser)\nmm/memfd_luo.c-477-{\nmm/memfd_luo.c:478:\tstruct memfd_luo_folio_ser folios_ser;\nmm/memfd_luo.c-479-\n--\nmm/memfd_luo.c-484-\nmm/memfd_luo.c:485:\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\nmm/memfd_luo.c-486-\t\tvfree(folios_ser);\n--\nmm/memfd_luo.c-492-\nmm/memfd_luo.c:493:static void memfd_luo_finish(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-494-{\nmm/memfd_luo.c:495:\tstruct memfd_luo_ser ser;\nmm/memfd_luo.c-496-\n--\nmm/memfd_luo.c-508-\nmm/memfd_luo.c:509:\tmemfd_luo_release_ser(ser);\nmm/memfd_luo.c-510-}\nmm/memfd_luo.c-511-\nmm/memfd_luo.c:512:static int memfd_luo_retrieve_folios(struct file file,\nmm/memfd_luo.c:513:\t\t\t\t struct memfd_luo_folio_ser folios_ser,\nmm/memfd_luo.c-514-\t\t\t\t u64 nr_folios)\n--\nmm/memfd_luo.c-523-\tfor (i = 0; i \u003c nr_folios; i++) {\nmm/memfd_luo.c:524:\t\tconst struct memfd_luo_folio_ser pfolio = \u0026folios_ser[i];\nmm/memfd_luo.c-525-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-595-\tfor (long j = i + 1; j \u003c nr_folios; j++) {\nmm/memfd_luo.c:596:\t\tconst struct memfd_luo_folio_ser pfolio = \u0026folios_ser[j];\nmm/memfd_luo.c-597-\t\tphys_addr_t phys;\n--\nmm/memfd_luo.c-612-\nmm/memfd_luo.c:613:static int memfd_luo_retrieve(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-614-{\nmm/memfd_luo.c:615:\tstruct memfd_luo_folio_ser folios_ser = NULL;\nmm/memfd_luo.c:616:\tstruct memfd_luo_ser ser;\nmm/memfd_luo.c-617-\tstruct file file;\n--\nmm/memfd_luo.c-659-\t /\nmm/memfd_luo.c:660:\texec_mode = memfd_luo_restore_exec_mode(ser-\u003eflags);\nmm/memfd_luo.c-661-\tfile-\u003ef_inode-\u003ei_mode \u0026= ~0111;\n--\nmm/memfd_luo.c-674-\t\t/* retrieve_folios() consumes every preserved data folio. /\nmm/memfd_luo.c:675:\t\terr = memfd_luo_retrieve_folios(file, folios_ser,\nmm/memfd_luo.c-676-\t\t\t\t\t\tser-\u003enr_folios);\n--\nmm/memfd_luo.c-691-\tif (folios_ser) {\nmm/memfd_luo.c:692:\t\tmemfd_luo_discard_folios(folios_ser, ser-\u003enr_folios);\nmm/memfd_luo.c-693-\t\tvfree(folios_ser);\n--\nmm/memfd_luo.c-699-release_ser:\nmm/memfd_luo.c:700:\tmemfd_luo_release_ser(ser);\nmm/memfd_luo.c-701-\treturn err;\n--\nmm/memfd_luo.c-703-\nmm/memfd_luo.c:704:static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler,\nmm/memfd_luo.c-705-\t\t\t\t struct file file)\n--\nmm/memfd_luo.c-716-\nmm/memfd_luo.c:717:static unsigned long memfd_luo_get_id(struct file file)\nmm/memfd_luo.c-718-{\n--\nmm/memfd_luo.c-721-\nmm/memfd_luo.c:722:static const struct liveupdate_file_ops memfd_luo_file_ops = {\nmm/memfd_luo.c:723:\t.freeze = memfd_luo_freeze,\nmm/memfd_luo.c:724:\t.unfreeze = memfd_luo_unfreeze,\nmm/memfd_luo.c:725:\t.finish = memfd_luo_finish,\nmm/memfd_luo.c:726:\t.retrieve = memfd_luo_retrieve,\nmm/memfd_luo.c:727:\t.preserve = memfd_luo_preserve,\nmm/memfd_luo.c:728:\t.unpreserve = memfd_luo_unpreserve,\nmm/memfd_luo.c:729:\t.can_preserve = memfd_luo_can_preserve,\nmm/memfd_luo.c:730:\t.get_id = memfd_luo_get_id,\nmm/memfd_luo.c-731-\t.owner = THIS_MODULE,\n--\nmm/memfd_luo.c-733-\nmm/memfd_luo.c:734:static struct liveupdate_file_handler memfd_luo_handler = {\nmm/memfd_luo.c:735:\t.ops = \u0026memfd_luo_file_ops,\nmm/memfd_luo.c-736-\t.compatible = MEMFD_LUO_FH_COMPATIBLE,\n--\nmm/memfd_luo.c-745- /\nmm/memfd_luo.c:746:static bool memfd_luo_can_preserve_v2(struct liveupdate_file_handler handler,\nmm/memfd_luo.c-747-\t\t\t\t struct file *file)\n--\nmm/memfd_luo.c-751-\nmm/memfd_luo.c:752:static const struct liveupdate_file_ops memfd_luo_file_ops_v2 = {\nmm/memfd_luo.c:753:\t.freeze = memfd_luo_freeze,\nmm/memfd_luo.c:754:\t.unfreeze = memfd_luo_unfreeze,\nmm/memfd_luo.c:755:\t.finish = memfd_luo_finish,\nmm/memfd_luo.c:756:\t.retrieve = memfd_luo_retrieve,\nmm/memfd_luo.c:757:\t.preserve = memfd_luo_preserve,\nmm/memfd_luo.c:758:\t.unpreserve = memfd_luo_unpreserve,\nmm/memfd_luo.c:759:\t.can_preserve = memfd_luo_can_preserve_v2,\nmm/memfd_luo.c:760:\t.get_id = memfd_luo_get_id,\nmm/memfd_luo.c-761-\t.owner = THIS_MODULE,\n--\nmm/memfd_luo.c-763-\nmm/memfd_luo.c:764:static struct liveupdate_file_handler memfd_luo_handler_v2 = {\nmm/memfd_luo.c:765:\t.ops = \u0026memfd_luo_file_ops_v2,\nmm/memfd_luo.c-766-\t.compatible = MEMFD_LUO_FH_COMPATIBLE_V2,\n--\nmm/memfd_luo.c-768-\nmm/memfd_luo.c:769:static int __init memfd_luo_init(void)\nmm/memfd_luo.c-770-{\n--\nmm/memfd_luo.c-772-\nmm/memfd_luo.c:773:\terr = liveupdate_register_file_handler(\u0026memfd_luo_handler);\nmm/memfd_luo.c-774-\tif (err) {\n--\nmm/memfd_luo.c-783-\nmm/memfd_luo.c:784:\terr = liveupdate_register_file_handler(\u0026memfd_luo_handler_v2);\nmm/memfd_luo.c-785-\tif (err) {\nmm/memfd_luo.c:786:\t\tliveupdate_unregister_file_handler(\u0026memfd_luo_handler);\nmm/memfd_luo.c-787-\n--\n\n" }
11/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26370 output: 35 thoughts: 50 Thoughts: Okay, let's dive into this `liveupdate` functionality. My first thought is always, "How is this exposed to userspace?" I need to understand the interface, the points of interaction. So, my instinct is to look at where userspace gets its hooks. I need to quickly understand how the userspace interacts with the liveupdate mechanism. I figure the first place to start is the obvious: I’ll check the kernel’s include files to see if there is a header file that defines the userspace API. Then, I'll go digging in the kernel itself, likely in `kernel/liveupdate/`. That should give me a good initial picture of what's going on. Let's see what's in `include/uapi/linux/liveupdate.h` and the `kernel/liveupdate/` directory.
12/2	2026/10/14 08:44	tool	grepper	0m Args: { "Expression": "LIVEUPDATE_SESSION", "PathPrefixes": [ "kernel/liveupdate/", "include/" ] } Results: { "Output": "include/linux/kho/abi/luo.h=131=struct luo_session_ser {\ninclude/linux/kho/abi/luo.h:132:\tchar name[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/linux/kho/abi/luo.h-133-\tstruct luo_file_set_ser file_set_ser;\n--\ninclude/uapi/linux/liveupdate.h-46-/* The maximum length of session name including null termination /\ninclude/uapi/linux/liveupdate.h:47:#define LIVEUPDATE_SESSION_NAME_LENGTH 64\ninclude/uapi/linux/liveupdate.h-48-\n--\ninclude/uapi/linux/liveupdate.h=57=enum {\n--\ninclude/uapi/linux/liveupdate.h-69- @name:\tInput; A null-terminated string for the session name, max\ninclude/uapi/linux/liveupdate.h:70: \t\tlength %LIVEUPDATE_SESSION_NAME_LENGTH including termination\ninclude/uapi/linux/liveupdate.h-71- \t\tcharacter.\n--\ninclude/uapi/linux/liveupdate.h=78=struct liveupdate_ioctl_create_session {\n--\ninclude/uapi/linux/liveupdate.h-80-\t__s32\t\tfd;\ninclude/uapi/linux/liveupdate.h:81:\t__u8\t\tname[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/uapi/linux/liveupdate.h-82-};\n--\ninclude/uapi/linux/liveupdate.h-103- * operations, such as restoring individual file descriptors with\ninclude/uapi/linux/liveupdate.h:104: * LIVEUPDATE_SESSION_RETRIEVE_FD.\ninclude/uapi/linux/liveupdate.h-105- \n--\ninclude/uapi/linux/liveupdate.h=113=struct liveupdate_ioctl_retrieve_session {\n--\ninclude/uapi/linux/liveupdate.h-115-\t__s32\t\tfd;\ninclude/uapi/linux/liveupdate.h:116:\t__u8\t\tname[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/uapi/linux/liveupdate.h-117-};\n--\ninclude/uapi/linux/liveupdate.h-124-/\ninclude/uapi/linux/liveupdate.h:125: struct liveupdate_session_preserve_fd - ioctl(LIVEUPDATE_SESSION_PRESERVE_FD)\ninclude/uapi/linux/liveupdate.h-126- * @size: Input; sizeof(struct liveupdate_session_preserve_fd)\n--\ninclude/uapi/linux/liveupdate.h-141- * This token confirms the FD is targeted for preservation and is required for\ninclude/uapi/linux/liveupdate.h:142: * the subsequent %LIVEUPDATE_SESSION_RETRIEVE_FD call after the live update.\ninclude/uapi/linux/liveupdate.h-143- \n--\ninclude/uapi/linux/liveupdate.h=148=struct liveupdate_session_preserve_fd {\n--\ninclude/uapi/linux/liveupdate.h-153-\ninclude/uapi/linux/liveupdate.h:154:#define LIVEUPDATE_SESSION_PRESERVE_FD\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-155-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_PRESERVE_FD)\n--\ninclude/uapi/linux/liveupdate.h-157-/\ninclude/uapi/linux/liveupdate.h:158: struct liveupdate_session_retrieve_fd - ioctl(LIVEUPDATE_SESSION_RETRIEVE_FD)\ninclude/uapi/linux/liveupdate.h-159- * @size: Input; sizeof(struct liveupdate_session_retrieve_fd)\n--\ninclude/uapi/linux/liveupdate.h=178=struct liveupdate_session_retrieve_fd {\n--\ninclude/uapi/linux/liveupdate.h-183-\ninclude/uapi/linux/liveupdate.h:184:#define LIVEUPDATE_SESSION_RETRIEVE_FD\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-185-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_RETRIEVE_FD)\n--\ninclude/uapi/linux/liveupdate.h-187-/*\ninclude/uapi/linux/liveupdate.h:188: struct liveupdate_session_finish - ioctl(LIVEUPDATE_SESSION_FINISH)\ninclude/uapi/linux/liveupdate.h-189- * @size: Input; sizeof(struct liveupdate_session_finish)\n--\ninclude/uapi/linux/liveupdate.h-196- * This ioctl must be called once all required file descriptors for the session\ninclude/uapi/linux/liveupdate.h:197: * have been successfully retrieved (using %LIVEUPDATE_SESSION_RETRIEVE_FD) and\ninclude/uapi/linux/liveupdate.h-198- * are fully restored from the userspace and kernel perspective.\n--\ninclude/uapi/linux/liveupdate.h=211=struct liveupdate_session_finish {\n--\ninclude/uapi/linux/liveupdate.h-215-\ninclude/uapi/linux/liveupdate.h:216:#define LIVEUPDATE_SESSION_FINISH\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-217-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FINISH)\n--\ninclude/uapi/linux/liveupdate.h-219-/*\ninclude/uapi/linux/liveupdate.h:220: struct liveupdate_session_get_name - ioctl(LIVEUPDATE_SESSION_GET_NAME)\ninclude/uapi/linux/liveupdate.h-221- * @size: Input; sizeof(struct liveupdate_session_get_name)\n--\ninclude/uapi/linux/liveupdate.h=230=struct liveupdate_session_get_name {\n--\ninclude/uapi/linux/liveupdate.h-232-\t__u32\t\treserved;\ninclude/uapi/linux/liveupdate.h:233:\t__u8\t\tname[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/uapi/linux/liveupdate.h-234-};\ninclude/uapi/linux/liveupdate.h-235-\ninclude/uapi/linux/liveupdate.h:236:#define LIVEUPDATE_SESSION_GET_NAME\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-237-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME)\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_session.c=373=static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c:374:\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\nkernel/liveupdate/luo_session.c-375-\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:376:\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\nkernel/liveupdate/luo_session.c-377-\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\nkernel/liveupdate/luo_session.c:378:\tIOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,\nkernel/liveupdate/luo_session.c-379-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:380:\tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\nkernel/liveupdate/luo_session.c-381-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_ALL),\n--\nkernel/liveupdate/luo_session.c=463=int luo_session_create(const char name, struct file filep)\nkernel/liveupdate/luo_session.c-464-{\nkernel/liveupdate/luo_session.c:465:\tsize_t len = strnlen(name, LIVEUPDATE_SESSION_NAME_LENGTH);\nkernel/liveupdate/luo_session.c-466-\tstruct luo_session session;\n--\nkernel/liveupdate/luo_session.c-468-\nkernel/liveupdate/luo_session.c:469:\tif (len == 0 \|\| len \u003e LIVEUPDATE_SESSION_NAME_LENGTH - 1)\nkernel/liveupdate/luo_session.c-470-\t\treturn -EINVAL;\n" }
13/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28949 output: 37 thoughts: 41 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Investigating the `luo_session_create` Call Path Alright, I'm trying to trace how this `luo_session_create` function is getting called. My initial instinct is to figure out if it's tied to some standard character device or a miscellaneous device. With Live Update being a potential source, let's start by looking at the kernel source, specifically something like `kernel/liveupdate/luo_core.c`, or something in that directory, if it's not the exact file name. That's the most logical place to begin digging. The device drivers might be using a character device or a misc device to expose the functionality. It's often the case that these Live Update components are part of such a setup. I'll need to confirm if it's a character device via ioctl, or a miscdevice. The goal is to rapidly determine the call hierarchy.
14/2	2026/10/14 08:44	tool	grepper	0m Args: { "Expression": "miscdevice\|alloc_chrdev\|file_operations", "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=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=387=static long luo_ioctl(struct file filep, unsigned int cmd, unsigned long arg)\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_session.c=401=static long luo_session_ioctl(struct file filep, unsigned int cmd,\n--\nkernel/liveupdate/luo_session.c-439-\nkernel/liveupdate/luo_session.c:440:static const struct file_operations luo_session_fops = {\nkernel/liveupdate/luo_session.c-441-\t.owner = THIS_MODULE,\n" }
15/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29631 output: 28 thoughts: 42 Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person: Initial Assessment: Liveupdate Device Discovery Well, isn't that interesting? A `/dev/liveupdate` miscdevice. That immediately sparks my curiosity. Given the name, I'm already anticipating this relates to some kind of live kernel update mechanism. The presence of this miscdevice is the starting point for a deeper dive. The next logical step, of course, is to ascertain the internal kernel name associated with this device. I need to understand which code is responsible for its creation and operation. Therefore, I need to know where I can find the information on the miscdev's name. I'll need to know which code created it, and what functions it exposes to userspace. I'll check `kernel/liveupdate/luo_core.c` and see what it's called internally. Knowing that internal name is the critical first step in truly understanding this live update functionality.
16/2	2026/10/14 08:44	tool	grepper	0m Args: { "Expression": "miscdev", "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=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=330=static int luo_open(struct inode inodep, struct file filep)\n--\nkernel/liveupdate/luo_core.c-333-\t\t\t\t\t\t struct luo_device_state,\nkernel/liveupdate/luo_core.c:334:\t\t\t\t\t\t miscdev);\nkernel/liveupdate/luo_core.c-335-\n--\nkernel/liveupdate/luo_core.c=348=static int luo_release(struct inode inodep, struct file filep)\n--\nkernel/liveupdate/luo_core.c-351-\t\t\t\t\t\t struct luo_device_state,\nkernel/liveupdate/luo_core.c:352:\t\t\t\t\t\t miscdev);\nkernel/liveupdate/luo_core.c-353-\tatomic_set(\u0026ldev-\u003ein_use, 0);\n--\nkernel/liveupdate/luo_core.c=426=static struct luo_device_state luo_dev = {\nkernel/liveupdate/luo_core.c:427:\t.miscdev = {\nkernel/liveupdate/luo_core.c-428-\t\t.minor = MISC_DYNAMIC_MINOR,\n--\nkernel/liveupdate/luo_core.c=435=static int __init liveupdate_ioctl_init(void)\n--\nkernel/liveupdate/luo_core.c-439-\nkernel/liveupdate/luo_core.c:440:\treturn misc_register(\u0026luo_dev.miscdev);\nkernel/liveupdate/luo_core.c-441-}\n" }
17/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30484 output: 39 thoughts: 17 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: Investigating the `.name` Attribute within `luo_dev` Alright, let's get down to brass tacks. I need to quickly ascertain the current state of the `.name` attribute within the `luo_dev` context. No fancy setup or preamble, I just want to know what's already set there. Is it null? A default value? Something dynamically assigned? The context is key here. I'm assuming that whatever library or framework `luo_dev` represents, it has a documented or expected behavior regarding the `.name` field. So, my primary focus is to bypass any assumptions and just grab the raw value currently configured for the object, whatever that may be. I'm going to start there, as I am trying to understand the system.
18/2	2026/10/14 08:44	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 425, "LineCount": 20 } Results: { "Contents": " 425:\t\n 426:\tstatic struct luo_device_state luo_dev = {\n 427:\t\t.miscdev = {\n 428:\t\t\t.minor = MISC_DYNAMIC_MINOR,\n 429:\t\t\t.name = \"liveupdate\",\n 430:\t\t\t.fops = \u0026luo_fops,\n 431:\t\t},\n 432:\t\t.in_use = ATOMIC_INIT(0),\n 433:\t};\n 434:\t\n 435:\tstatic int __init liveupdate_ioctl_init(void)\n 436:\t{\n 437:\t\tif (!liveupdate_enabled())\n 438:\t\t\treturn 0;\n 439:\t\n 440:\t\treturn misc_register(\u0026luo_dev.miscdev);\n 441:\t}\n 442:\tlate_initcall(liveupdate_ioctl_init);\n" }
19/2	2026/10/14 08:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30984 output: 35 thoughts: 13 Thoughts: Okay, let's dive into this. Here's my take on those thoughts, as if they're my own: Investigating `liveupdate_enabled()` Right, let's get down to brass tacks. I need to understand what `liveupdate_enabled()` is actually doing. It's a key function, I can tell, and I need to fully grasp its role in this system. I'm going to carefully dissect its implementation and trace its behavior. My expertise allows me to quickly identify potential areas of concern and optimize my understanding. This is crucial for me to move forward with this project, I need to know the inner workings before I can make effective decisions. My analysis starts now.
20/2	2026/10/14 08:45	tool	grepper	0m Args: { "Expression": "liveupdate_enabled", "PathPrefixes": [ "kernel/liveupdate/", "include/" ] } Results: { "Output": "include/linux/liveupdate.h=218=struct liveupdate_flb {\n--\ninclude/linux/liveupdate.h-228-/* Return true if live update orchestrator is enabled /\ninclude/linux/liveupdate.h:229:bool liveupdate_enabled(void);\ninclude/linux/liveupdate.h-230-\n--\ninclude/linux/liveupdate.h=245=int liveupdate_flb_get_outgoing(struct liveupdate_flb flb, void objp);\n--\ninclude/linux/liveupdate.h-248-\ninclude/linux/liveupdate.h:249:static inline bool liveupdate_enabled(void)\ninclude/linux/liveupdate.h-250-{\n--\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\");\n--\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=220=int liveupdate_reboot(void)\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- \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=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_file.c=874=int liveupdate_register_file_handler(struct liveupdate_file_handler fh)\n--\nkernel/liveupdate/luo_file.c-878-\nkernel/liveupdate/luo_file.c:879:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_file.c-880-\t\treturn -EOPNOTSUPP;\n--\nkernel/liveupdate/luo_file.c=920=void liveupdate_unregister_file_handler(struct liveupdate_file_handler fh)\nkernel/liveupdate/luo_file.c-921-{\nkernel/liveupdate/luo_file.c:922:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_file.c-923-\t\treturn;\n--\nkernel/liveupdate/luo_flb.c=359=void luo_flb_unregister_all(struct liveupdate_file_handler fh)\n--\nkernel/liveupdate/luo_flb.c-363-\nkernel/liveupdate/luo_flb.c:364:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_flb.c-365-\t\treturn;\n--\nkernel/liveupdate/luo_flb.c=394=int liveupdate_register_flb(struct liveupdate_file_handler fh,\n--\nkernel/liveupdate/luo_flb.c-402-\nkernel/liveupdate/luo_flb.c:403:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_flb.c-404-\t\treturn -EOPNOTSUPP;\n--\nkernel/liveupdate/luo_flb.c=474=void liveupdate_unregister_flb(struct liveupdate_file_handler fh,\n--\nkernel/liveupdate/luo_flb.c-476-{\nkernel/liveupdate/luo_flb.c:477:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_flb.c-478-\t\treturn;\n--\nkernel/liveupdate/luo_flb.c=503=int liveupdate_flb_get_incoming(struct liveupdate_flb flb, void *objp)\n--\nkernel/liveupdate/luo_flb.c-506-\nkernel/liveupdate/luo_flb.c:507:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_flb.c-508-\t\treturn -EOPNOTSUPP;\n--\nkernel/liveupdate/luo_flb.c=539=int liveupdate_flb_get_outgoing(struct liveupdate_flb flb, void **objp)\n--\nkernel/liveupdate/luo_flb.c-542-\nkernel/liveupdate/luo_flb.c:543:\tif (!liveupdate_enabled())\nkernel/liveupdate/luo_flb.c-544-\t\treturn -EOPNOTSUPP;\n" }
21/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 32686 output: 39 thoughts: 39 Thoughts: Here's my summary, as if I were thinking these thoughts: Analyzing `liveupdate_enabled()` Implementation Okay, time to dig into the heart of the matter. I need to understand how the `liveupdate_enabled()` function is implemented within the Live Update framework. I'm going to jump straight into the code, specifically lines 236 through 260 of `kernel/liveupdate/luo_core.c`. That should give me the core logic behind the enabling or disabling of Live Updates. I'm expecting to see checks for configuration parameters, perhaps some global state variables, and likely some error handling or security-related considerations in those lines. Understanding this function's logic is crucial for assessing its behavior, potential vulnerabilities, or its interaction with other components of the LU system. Let's get to it.
22/2	2026/10/14 08:45	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 235, "LineCount": 30 } Results: { "Contents": " 235:\t\n 236:\t/*\n 237:\t liveupdate_enabled - Check if the live update feature is enabled.\n 238:\t \n 239:\t This function returns the state of the live update feature flag, which\n 240:\t * can be controlled via the ``liveupdate`` kernel command-line parameter.\n 241:\t \n 242:\t @return true if live update is enabled, false otherwise.\n 243:\t /\n 244:\tbool liveupdate_enabled(void)\n 245:\t{\n 246:\t\treturn luo_global.enabled;\n 247:\t}\n 248:\t\n 249:\t/\n 250:\t DOC: LUO ioctl Interface\n 251:\t \n 252:\t The IOCTL user-space control interface for the LUO subsystem.\n 253:\t * It registers a character device, typically found at ``/dev/liveupdate``,\n 254:\t * which allows a userspace agent to manage the LUO state machine and its\n 255:\t * associated resources, such as preservable file descriptors.\n 256:\t \n 257:\t To ensure that the state machine is controlled by a single entity, access\n 258:\t * to this device is exclusive: only one process is permitted to have\n 259:\t * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will\n 260:\t * fail with -EBUSY until the first process closes its file descriptor.\n 261:\t * This singleton model simplifies state management by preventing conflicting\n 262:\t * commands from multiple userspace agents.\n 263:\t */\n 264:\t\n" }
23/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 33397 output: 32 thoughts: 16 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and written as if they were my own: Investigating the Initialization of `luo_global.enabled` Alright, let's dive into this. I need to understand the initial state of `luo_global.enabled`. Where is this variable being set, and under what circumstances? It’s fundamental to whatever the system is doing, or I wouldn't have to look at it. I need to trace its initialization path. Is it coming from a configuration file, a hardcoded default, or perhaps derived from some external factor? Are there any conditional assignments based on the environment or runtime parameters? Are there any implicit dependencies I need to be aware of? Are there any potential race conditions if this is initialized in a multithreaded environment? The goal is to fully grasp its starting value and to see if there are any gotchas in the setup. That's the baseline, the foundation I need before I can assess any potential issues or optimize the related code. Let me just open up the source and see what I can find.
24/2	2026/10/14 08:45	tool	grepper	0m Args: { "Expression": "luo_global.enabled", "PathPrefixes": [ "kernel/liveupdate/" ] } 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" }
25/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34212 output: 32 thoughts: 29 Thoughts: Okay, let's break this down. Investigating the `luo_global` Variable Right, so I need to understand how `luo_global` is handled, specifically within the context of `CONFIG_LIVEUPDATE`. My immediate question is whether `luo_global` gets implicitly set to true if `CONFIG_LIVEUPDATE` is enabled. That would be a logical default behavior, given the implications of live updates. It's a key detail to understand how these functionalities interrelate and any potential dependencies. I’ll need to trace back to where `luo_global` is declared and see if there is any conditional logic related to `CONFIG_LIVEUPDATE` governing its initialization. Understanding the default behavior is fundamental to understanding any code.
26/2	2026/10/14 08:45	tool	grepper	0m Args: { "Expression": "luo_global\\b", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_core.c=67=static struct {\n--\nkernel/liveupdate/luo_core.c-70-\tu64 liveupdate_num;\nkernel/liveupdate/luo_core.c:71:} luo_global;\nkernel/liveupdate/luo_core.c-72-\n--\nkernel/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-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=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=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-177-\nkernel/liveupdate/luo_core.c:178:\tluo_global.luo_ser_out = luo_ser;\nkernel/liveupdate/luo_core.c-179-\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" }
27/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35401 output: 38 thoughts: 25 Thoughts: Okay, let's dive into this. I'm focusing on lines 60-77 of `kernel/liveupdate/luo_core.c`. My initial thought is to quickly grasp the context. What's this section doing within the larger Live Update framework? Is it handling state transitions, data management, error checking, or something else entirely? Given the "luo_core" in the filename, I'm expecting this to be a core function, likely touching a fundamental part of the Live Update process. I need to quickly ascertain the function's purpose. What actions are executed? Are we looking at handling communication with some other part of the system? Are we updating any data structures? Is the code straightforward, or are there layers of abstraction to dig through? My goal is to synthesize the intent and its connection to the overall design. Are any important variables declared within this segment? Is there anything that could be optimized to minimize the effects on the running system? I also need to make sure this section is free from any obvious concurrency issues. I will also make sure to check what happens if it is not handled properly.
28/2	2026/10/14 08:45	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 60, "LineCount": 20 } Results: { "Contents": " 60:\t#include \u003clinux/rwsem.h\u003e\n 61:\t#include \u003clinux/sizes.h\u003e\n 62:\t#include \u003clinux/string.h\u003e\n 63:\t\n 64:\t#include \"kexec_handover_internal.h\"\n 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" }
29/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35968 output: 38 thoughts: 52 Thoughts: Okay, let me think this through. Investigating the `luo_global.enabled` Initialization Wait a second, how is this `luo_global.enabled` variable getting set? I know I can override it on the command line, but what's the default or an early initialization path? I need to understand this better. I vaguely recall there being a chance it is set through an early parameter. Alright, time to get to the source. Specifically, my intuition tells me this is likely handled within the `kernel/liveupdate/luo_core.c` file. I'm going to jump straight to lines 80 through 100 within that file. That's usually where initialization and the core setup logic resides. I'm betting that's where I'll find the answer to my question. Let's see what that section reveals. I'll be looking for any hints about parameter parsing or conditional assignments related to `luo_global.enabled` in that range.
30/2	2026/10/14 08:45	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 78, "LineCount": 35 } Results: { "Contents": " 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 105:\t\t\t}\n 106:\t\n 107:\t\t\treturn 0;\n 108:\t\t}\n 109:\t\n 110:\t\tif (len \u003c sizeof(luo_ser)) {\n 111:\t\t\tpr_err(\"LUO state is too small (%zu \u003c %zu)\\n\", len, sizeof(*luo_ser));\n 112:\t\t\treturn -EINVAL;\n" }
31/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36792 output: 39 thoughts: 66 Thoughts: Here's my summary, as if I were thinking these things: Debugging a Live Update Initialization Issue Okay, first things first. I need to refresh my memory on the `luo_global.enabled` flag. Right, it's disabled by default, isn't it? Unless we explicitly pass in some kind of `liveupdate` command-line argument... something like `liveupdate=on` or `liveupdate=1`? I need to confirm that. I'm betting the root of the problem lies in the initialization sequence. So, the next thing I'm going to do is dive into the code. Specifically, I need to get my bearings in `kernel/liveupdate/luo_core.c`. I need to zero in on the initialization sequence, looking at the code around the `late_initcall` function or `liveupdate_early_init` – that's where the critical initialization logic is located. Hopefully, I'll find the logic that governs the initial state of this `luo_global.enabled` flag and where the command line arguments are being parsed and processed. That should give me a good handle on why it's not being set correctly.
32/2	2026/10/14 08:45	tool	read-file	0m Args: { "File": "kernel/liveupdate/luo_core.c", "FirstLine": 130, "LineCount": 70 } Results: { "Contents": " 130:\t\n 131:\t\terr = 0;\n 132:\t\n 133:\tout_free_ser:\n 134:\t\tkho_restore_free(luo_ser);\n 135:\t\treturn err;\n 136:\t}\n 137:\t\n 138:\tstatic int __init liveupdate_early_init(void)\n 139:\t{\n 140:\t\tint err;\n 141:\t\n 142:\t\terr = luo_early_startup();\n 143:\t\tif (err) {\n 144:\t\t\tluo_global.enabled = false;\n 145:\t\t\tluo_restore_fail(\"The incoming tree failed to initialize properly [%pe], disabling live update\\n\",\n 146:\t\t\t\t\t ERR_PTR(err));\n 147:\t\t}\n 148:\t\n 149:\t\treturn err;\n 150:\t}\n 151:\tearly_initcall(liveupdate_early_init);\n 152:\t\n 153:\t/* Called during boot to create outgoing LUO state /\n 154:\tstatic int __init luo_state_setup(void)\n 155:\t{\n 156:\t\tstruct luo_ser luo_ser;\n 157:\t\tint err;\n 158:\t\n 159:\t\tluo_ser = kho_alloc_preserve(sizeof(luo_ser));\n 160:\t\tif (IS_ERR(luo_ser)) {\n 161:\t\t\tpr_err(\"failed to allocate/preserve LUO state memory\\n\");\n 162:\t\t\treturn PTR_ERR(luo_ser);\n 163:\t\t}\n 164:\t\n 165:\t\tstrscpy(luo_ser-\u003ecompatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser-\u003ecompatible));\n 166:\t\tluo_ser-\u003eliveupdate_num = luo_global.liveupdate_num + 1;\n 167:\t\n 168:\t\tluo_session_setup_outgoing(\u0026luo_ser-\u003esessions_pa);\n 169:\t\n 170:\t\terr = luo_flb_setup_outgoing(\u0026luo_ser-\u003eflbs_pa);\n 171:\t\tif (err)\n 172:\t\t\tgoto exit_free_luo_ser;\n 173:\t\n 174:\t\terr = kho_add_subtree(LUO_KHO_ENTRY_NAME, luo_ser, sizeof(luo_ser));\n 175:\t\tif (err)\n 176:\t\t\tgoto exit_free_luo_ser;\n 177:\t\n 178:\t\tluo_global.luo_ser_out = luo_ser;\n 179:\t\n 180:\t\treturn 0;\n 181:\t\n 182:\texit_free_luo_ser:\n 183:\t\tkho_unpreserve_free(luo_ser);\n 184:\t\tpr_err(\"failed to prepare LUO state: %d\\n\", err);\n 185:\t\n 186:\t\treturn err;\n 187:\t}\n 188:\t\n 189:\t/\n 190:\t late initcall because it initializes the outgoing tree that is needed only\n 191:\t * once userspace starts using /dev/liveupdate.\n 192:\t */\n 193:\tstatic int __init luo_late_startup(void)\n 194:\t{\n 195:\t\tint err;\n 196:\t\n 197:\t\tif (!liveupdate_enabled())\n 198:\t\t\treturn 0;\n 199:\t\n" }
33/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38133 output: 36 thoughts: 20 Thoughts: Here's my thought process, as if I were considering this myself: Investigating the KHO Enablement Okay, so I'm trying to figure out the status of KHO – how it's currently enabled. My initial thought is, let's cut right to the chase and directly check the enabling condition. The most straightforward approach is to call the dedicated function. I'll need to use the `kho_is_enabled()` function. That should give me a definitive answer as to whether this particular feature or module is active at this moment. Let's see what that yields.
34/2	2026/10/14 08:45	tool	grepper	0m Args: { "Expression": "kho_is_enabled", "PathPrefixes": [ "kernel/liveupdate/", "include/" ] } Results: { "Output": "include/linux/kexec_handover.h=17=struct page;\n--\ninclude/linux/kexec_handover.h-19-#ifdef CONFIG_KEXEC_HANDOVER\ninclude/linux/kexec_handover.h:20:bool kho_is_enabled(void);\ninclude/linux/kexec_handover.h-21-bool is_kho_boot(void);\n--\ninclude/linux/kexec_handover.h=41=void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys,\n--\ninclude/linux/kexec_handover.h-43-#else\ninclude/linux/kexec_handover.h:44:static inline bool kho_is_enabled(void)\ninclude/linux/kexec_handover.h-45-{\n--\nkernel/liveupdate/kexec_handover.c=58=static bool kho_enable __ro_after_init = IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);\nkernel/liveupdate/kexec_handover.c-59-\nkernel/liveupdate/kexec_handover.c:60:bool kho_is_enabled(void)\nkernel/liveupdate/kexec_handover.c-61-{\n--\nkernel/liveupdate/kexec_handover.c-63-}\nkernel/liveupdate/kexec_handover.c:64:EXPORT_SYMBOL_GPL(kho_is_enabled);\nkernel/liveupdate/kexec_handover.c-65-\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" }
35/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38806 output: 33 thoughts: 101 Thoughts: Investigating the KEXEC Handover and Live Update Enablement Okay, let's dive in. I need to understand how the KEXEC handover feature interacts with live updates, specifically, how it's enabled and disabled. My first point of reference is the `kernel/liveupdate/kexec_handover.c` file. I see the `kho_enable` variable, declared as `static bool kho_enable __ro_after_init = IS_ENABLED(CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT);`. That's straightforward; it's likely tied to a default configuration option. However, the bigger question in my mind right now is the relationship with `luo_global.enabled`. How exactly is that variable set? If it's not strictly a command-line option (and I'm fairly certain I've seen it used implicitly), then I need to trace back its initialization. Let's head over to `kernel/liveupdate/luo_core.c` and search for the definition and uses of `enabled` within the context of live update. That's where the control logic must reside. I need to see how the system determines whether a live update can, or will, be executed. Let's see what we can find.
36/2	2026/10/14 08:45	tool	grepper	0m Args: { "Expression": "enabled", "PathPrefixes": [ "kernel/liveupdate/luo_core.c" ] } Results: { "Output": "kernel/liveupdate/luo_core.c=67=static struct {\nkernel/liveupdate/luo_core.c:68:\tbool enabled;\nkernel/liveupdate/luo_core.c-69-\tstruct luo_ser luo_ser_out;\n--\nkernel/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-90-\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;\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-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-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=220=int liveupdate_reboot(void)\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- \n--\nkernel/liveupdate/luo_core.c-241- \nkernel/liveupdate/luo_core.c:242: * @return true if live update is enabled, false otherwise.\nkernel/liveupdate/luo_core.c-243- */\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--\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" }
37/2	2026/10/14 08:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40275 output: 38 thoughts: 1291 Thoughts: Deep Dive into Live Update Logic and Potential Side Effects Okay, first things first. I need to get a handle on this `luo_global.enabled` flag. It's a static bool, initialized to false unless `liveupdate=on` or `liveupdate=1` is passed on the kernel command line. I was wondering if there was a Kconfig option that enabled `LIVEUPDATE` by default. Let me check `kernel/liveupdate/Kconfig`. No, wait... there was a `KEXEC_HANDOVER_ENABLE_DEFAULT` option, but not one specifically for `LIVEUPDATE`. Alright, I should try to understand where command-line arguments are set, or if something else is causing a trigger for the logic in question. Now, to really understand this, I need to look at the code that's actually being touched by this patch, line by line. Here's what I'm seeing: 1. `mm/memfd.c`: The function `memfd_add_seals` is being modified. Now, if the file is a shmem file and its seal state is frozen, it'll return an error (`-EPERM`). 2. `mm/shmem.c`: I see changes to `shmem_setattr()` and `shmem_set_acl()`. In `shmem_setattr()`, I notice a similar pattern: if the inode's seal state is frozen or the `F_SEAL_EXEC` is set, and the mode is being changed (e.g., `chmod`), it will return an error. `shmem_set_acl()` is particularly interesting. It appears to be new, replacing `simple_set_acl` in various `shmem_inode_operations` structures. Wait! This is crucial. Whenever a user is setting a POSIX ACL (via `setxattr`, `fsetxattr`, or `setfacl`) on any tmpfs/shmem file, this `shmem_set_acl` function will be called. I need to be sure. I'm checking the before and after versions of `.set_acl` in `mm/shmem.c`. Correct, `shmem_set_acl` is now conditionally used if `CONFIG_TMPFS_POSIX_ACL` is enabled, and if it is used, it adds the condition to return `-EPERM` if the ACL is an access type and the file is frozen. And it's also clear that even without live update enabled, it will be executed if POSIX ACLs are set on tmpfs files. The execution check happens on `chmod`/`fchmod`/`setattr` operations. The condition has changed from `if ((info->seals & F_SEAL_EXEC) && (attr->ia_valid & ATTR_MODE))` to `if ((attr->ia_valid & ATTR_MODE) && ((info->seals & F_SEAL_EXEC) \|\| shmem_seal_state_frozen(inode))`. Also, the function `memfd_add_seals` will be executed in every call to `fcntl(fd, F_ADD_SEALS, ...)` on a memfd, and this condition is `if (shmem_file(file) && shmem_seal_state_frozen(inode))`. I need to dig into the `mm/memfd_luo.c` file and understand how LUO is actually being used, and how `memfd_luo_freeze`, `preserve`, and `retrieve` are called. I'm also going to search for where `memfd_luo_handler` or `liveupdate_file_ops` are used within the kernel to fully understand the flow.
38/2	2026/10/14 08:46	tool	grepper	0m Args: { "Expression": "\\.freeze\|\\.unfreeze\|\\.preserve\|\\.retrieve", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_file.c-30- * actual reboot transition.\nkernel/liveupdate/luo_file.c:31: * - unpreserve(): Cleans up any resources allocated by .preserve(), called\nkernel/liveupdate/luo_file.c-32- * if the preservation process is aborted before the reboot (i.e. session is\n--\nkernel/liveupdate/luo_file.c-36- * the file anymore.\nkernel/liveupdate/luo_file.c:37: * - unfreeze(): Undoes the actions of .freeze(), called if the live update\nkernel/liveupdate/luo_file.c-38- * is aborted after the freeze phase.\n--\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\nkernel/liveupdate/luo_file.c-49- * luo_file to track the live state.\n--\nkernel/liveupdate/luo_file.c-51- * 2. Freeze (Pre-Reboot): Just before the kexec, luo_file_freeze() is called.\nkernel/liveupdate/luo_file.c:52: * It iterates through all preserved files, calls their respective .freeze()\nkernel/liveupdate/luo_file.c-53- * operation, and serializes their final metadata (compatible string, token,\n--\nkernel/liveupdate/luo_file.c-63- * restore file descriptors by providing a token. luo_retrieve_file()\nkernel/liveupdate/luo_file.c:64: * searches for the matching token, calls the handler's .retrieve() op to\nkernel/liveupdate/luo_file.c-65- * re-create the 'struct file', and returns a new FD. Files can be\n--\nkernel/liveupdate/luo_file.c-81- \nkernel/liveupdate/luo_file.c:82: 2. Freeze Failure: During the reboot() syscall, if any handler's .freeze()\nkernel/liveupdate/luo_file.c:83: * op fails, the .unfreeze() op is invoked on all previously successful\nkernel/liveupdate/luo_file.c-84- * freezes to roll back their state. The reboot() syscall then returns an\n--\nkernel/liveupdate/luo_file.c=119=static DEFINE_XARRAY(luo_preserved_files);\n--\nkernel/liveupdate/luo_file.c-128- * @serialized_data: The opaque u64 handle to the serialized state of the file.\nkernel/liveupdate/luo_file.c:129: * This handle is passed back to the handler's .freeze(),\nkernel/liveupdate/luo_file.c:130: * .retrieve(), and .finish() callbacks, allowing it to track\nkernel/liveupdate/luo_file.c-131- * and update its serialized state across phases.\nkernel/liveupdate/luo_file.c-132- * @private_data: Pointer to the private data for the file used to hold runtime\nkernel/liveupdate/luo_file.c:133: * state that is not preserved. Set by the handler's .preserve()\nkernel/liveupdate/luo_file.c-134- * callback, and must be freed in the handler's .unpreserve()\n--\nkernel/liveupdate/luo_file.c-151- * to link a 'struct file' to its corresponding handler, a user-provided token,\nkernel/liveupdate/luo_file.c:152: * and the serialized state handle returned by the handler's .preserve()\nkernel/liveupdate/luo_file.c-153- * operation.\n--\nkernel/liveupdate/luo_file.c-156- * field, which holds a handle to the file's serialized state, may be updated\nkernel/liveupdate/luo_file.c:157: * during the .freeze() callback before being serialized for the next kernel.\nkernel/liveupdate/luo_file.c-158- * After reboot, these structures are recreated by luo_file_deserialize() and\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-209- compatible with the given @fd.\nkernel/liveupdate/luo_file.c:210: * 4. Calls the handler's .preserve() operation, which saves the file's state\nkernel/liveupdate/luo_file.c-211- * and returns an opaque private data handle.\n--\nkernel/liveupdate/luo_file.c-227- * -ENOMEM on memory allocation failure.\nkernel/liveupdate/luo_file.c:228: * Other erros might be returned by .preserve().\nkernel/liveupdate/luo_file.c-229- /\n--\nkernel/liveupdate/luo_file.c=406=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-433- \nkernel/liveupdate/luo_file.c:434: 1. Freezes the File: It calls the handler's .freeze() callback for each\nkernel/liveupdate/luo_file.c-435- * file. This gives the handler a final opportunity to quiesce the device or\n--\nkernel/liveupdate/luo_file.c-444- * Error Handling (Rollback):\nkernel/liveupdate/luo_file.c:445: * This function is atomic. If any handler's .freeze() operation fails, the\nkernel/liveupdate/luo_file.c-446- * entire live update is aborted. The __luo_file_unfreeze() helper is\nkernel/liveupdate/luo_file.c:447: * immediately called to invoke the .unfreeze() op on all files that were\nkernel/liveupdate/luo_file.c-448- * successfully frozen before the point of failure, rolling them back to a\n--\nkernel/liveupdate/luo_file.c=455=int luo_file_freeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-511- signals the helper to iterate through all files in the file_set and call\nkernel/liveupdate/luo_file.c:512: * their respective .unfreeze() handler callbacks.\nkernel/liveupdate/luo_file.c-513- \n--\nkernel/liveupdate/luo_file.c=517=void luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-549- * -ENOENT if no file with the matching token is found.\nkernel/liveupdate/luo_file.c:550: * Any error code returned by the handler's .retrieve() op.\nkernel/liveupdate/luo_file.c-551- /\n--\nkernel/liveupdate/luo_file.c=612=static int luo_file_can_finish_one(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-624-\t\targs.serialized_data = luo_file-\u003eserialized_data;\nkernel/liveupdate/luo_file.c:625:\t\targs.retrieve_status = luo_file-\u003eretrieve_status;\nkernel/liveupdate/luo_file.c-626-\t\tcan_finish = luo_file-\u003efh-\u003eops-\u003ecan_finish(\u0026args);\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-641-\targs.serialized_data = luo_file-\u003eserialized_data;\nkernel/liveupdate/luo_file.c:642:\targs.retrieve_status = luo_file-\u003eretrieve_status;\nkernel/liveupdate/luo_file.c-643-\n--\nkernel/liveupdate/luo_flb.c-28- \nkernel/liveupdate/luo_flb.c:29: * - .preserve(): Called for the first file. Saves global state.\nkernel/liveupdate/luo_flb.c-30- * - .unpreserve(): Called for the last file (if aborted pre-reboot).\nkernel/liveupdate/luo_flb.c:31: * - .retrieve(): Called on-demand in the new kernel to restore the state.\nkernel/liveupdate/luo_flb.c-32- * - .finish(): Called for the last file in the new kernel for cleanup.\n--\nkernel/liveupdate/luo_flb.c=158=static int luo_flb_retrieve_one(struct liveupdate_flb flb)\n--\nkernel/liveupdate/luo_flb.c-170-\nkernel/liveupdate/luo_flb.c:171:\tif (private-\u003eincoming.retrieved)\nkernel/liveupdate/luo_flb.c-172-\t\treturn 0;\n--\nkernel/liveupdate/luo_flb.c-201-\tprivate-\u003eincoming.obj = args.obj;\nkernel/liveupdate/luo_flb.c:202:\tprivate-\u003eincoming.retrieved = true;\nkernel/liveupdate/luo_flb.c-203-\n--\nkernel/liveupdate/luo_flb.c=207=void liveupdate_flb_put_incoming(struct liveupdate_flb flb)\n--\nkernel/liveupdate/luo_flb.c-215-\nkernel/liveupdate/luo_flb.c:216:\t\tif (!private-\u003eincoming.retrieved) {\nkernel/liveupdate/luo_flb.c-217-\t\t\tint err = luo_flb_retrieve_one(flb);\n--\nkernel/liveupdate/luo_flb.c-239- * handler. It increments the reference count for each FLB. If the count becomes\nkernel/liveupdate/luo_flb.c:240: * 1, it triggers the FLB's .preserve() callback to save the global state.\nkernel/liveupdate/luo_flb.c-241- \nkernel/liveupdate/luo_flb.c:242: This operation is atomic. If any FLB's .preserve() op fails, it will roll\nkernel/liveupdate/luo_flb.c-243- * back by calling .unpreserve() on any FLBs that were successfully preserved\n--\nkernel/liveupdate/luo_flb.c=474=void liveupdate_unregister_flb(struct liveupdate_file_handler fh,\n--\nkernel/liveupdate/luo_flb.c-493- If this is the first time the object is requested in the new kernel, this\nkernel/liveupdate/luo_flb.c:494: * function will trigger the FLB's .retrieve() callback to reconstruct the\nkernel/liveupdate/luo_flb.c-495- * object from its preserved state. Subsequent calls will return the same\n--\nkernel/liveupdate/luo_flb.c=503=int liveupdate_flb_get_incoming(struct liveupdate_flb flb, void objp)\n--\nkernel/liveupdate/luo_flb.c-533- This function assumes the object has already been created by the FLB's\nkernel/liveupdate/luo_flb.c:534: * .preserve() callback, which is triggered when the first dependent file\nkernel/liveupdate/luo_flb.c-535- * is preserved.\n" }
39/2	2026/10/14 08:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 45454 output: 32 thoughts: 34 Thoughts: Okay, here's my interpretation of those thoughts, presented as a summary from my perspective as a field expert: Investigating the `luo_file_freeze` Function Alright, I need to get a clear picture of how `luo_file_freeze` is being utilized in this system. Specifically, I need to understand the trigger. When exactly does this freezing process occur? It's crucial for understanding the overall behavior and potentially pinpointing performance bottlenecks or unexpected side effects. Therefore, my immediate course of action is to conduct a thorough search for every instance of `luo_file_freeze` within the codebase. This initial search will give me the contextual calls and understand the execution flow. I need to know the circumstances leading to its invocation. That will lead to a better understand of the overall process.
40/2	2026/10/14 08:46	tool	grepper	0m Args: { "Expression": "luo_file_freeze", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_file.c-50- \nkernel/liveupdate/luo_file.c:51: 2. Freeze (Pre-Reboot): Just before the kexec, luo_file_freeze() is called.\nkernel/liveupdate/luo_file.c-52- * It iterates through all preserved files, calls their respective .freeze()\n--\nkernel/liveupdate/luo_file.c=333=void luo_file_unpreserve_files(struct luo_file_set file_set)\n--\nkernel/liveupdate/luo_file.c-365-\nkernel/liveupdate/luo_file.c:366:static int luo_file_freeze_one(struct luo_file_set file_set,\nkernel/liveupdate/luo_file.c-367-\t\t\t struct luo_file luo_file)\n--\nkernel/liveupdate/luo_file.c=406=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-422-/*\nkernel/liveupdate/luo_file.c:423: luo_file_freeze - Freezes all preserved files and serializes their metadata.\nkernel/liveupdate/luo_file.c-424- * @file_set: The file_set whose files are to be frozen.\n--\nkernel/liveupdate/luo_file.c-454- /\nkernel/liveupdate/luo_file.c:455:int luo_file_freeze(struct luo_file_set file_set,\nkernel/liveupdate/luo_file.c-456-\t\t struct luo_file_set_ser file_set_ser)\n--\nkernel/liveupdate/luo_file.c-475-\nkernel/liveupdate/luo_file.c:476:\t\terr = luo_file_freeze_one(file_set, luo_file);\nkernel/liveupdate/luo_file.c-477-\t\tif (err \u003c 0) {\n--\nkernel/liveupdate/luo_file.c-507- freeze phase has begun but must be aborted. It is the counterpart to\nkernel/liveupdate/luo_file.c:508: * luo_file_freeze().\nkernel/liveupdate/luo_file.c-509- \n--\nkernel/liveupdate/luo_file.c-514- Context: This is called when the live update is aborted during\nkernel/liveupdate/luo_file.c:515: * the reboot() syscall, after luo_file_freeze() has been called.\nkernel/liveupdate/luo_file.c-516- /\n--\nkernel/liveupdate/luo_internal.h=88=void luo_file_unpreserve_files(struct luo_file_set file_set);\nkernel/liveupdate/luo_internal.h:89:int luo_file_freeze(struct luo_file_set file_set,\nkernel/liveupdate/luo_internal.h-90-\t\t struct luo_file_set_ser file_set_ser);\n--\nkernel/liveupdate/luo_session.c=229=static int luo_session_freeze_one(struct luo_session *session,\n--\nkernel/liveupdate/luo_session.c-232-\tguard(mutex)(\u0026session-\u003emutex);\nkernel/liveupdate/luo_session.c:233:\treturn luo_file_freeze(\u0026session-\u003efile_set, \u0026ser-\u003efile_set_ser);\nkernel/liveupdate/luo_session.c-234-}\n" }
41/2	2026/10/14 08:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 46631 output: 41 thoughts: 18 Thoughts: Okay, here's my summary, tailored for an expert audience, as if I'm thinking these things myself: Tracing the Execution Path of `luo_session_freeze_one` Alright, time to dig in. The immediate task is to understand the calling contexts of `luo_session_freeze_one`. It's a key function, and understanding where it's invoked is crucial to grasping its role in the overall session management architecture. I need to trace its call graph to get a precise picture of its operational environment. No point just jumping to the source code without understanding how this function fits into the bigger picture. Let's start with a cross-reference search. I'll need to identify all call sites, paying close attention to any conditional logic or parameter passing that might be significant. I'm looking for clues about the triggers for this freeze operation. Any potential race conditions? Concurrency issues? Security implications? I'll be meticulously examining the surrounding code in each call site to get the full story. This initial step will dictate the strategy for further analysis.
42/2	2026/10/14 08:46	tool	grepper	0m Args: { "Expression": "luo_session_freeze_one\|luo_session_freeze", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_session.c=222=static void luo_session_unfreeze_one(struct luo_session session,\n--\nkernel/liveupdate/luo_session.c-228-\nkernel/liveupdate/luo_session.c:229:static int luo_session_freeze_one(struct luo_session session,\nkernel/liveupdate/luo_session.c-230-\t\t\t\t struct luo_session_ser *ser)\n--\nkernel/liveupdate/luo_session.c=634=int luo_session_serialize(void)\n--\nkernel/liveupdate/luo_session.c-655-\nkernel/liveupdate/luo_session.c:656:\t\terr = luo_session_freeze_one(session, ser);\nkernel/liveupdate/luo_session.c-657-\t\tif (err) {\n" }
43/2	2026/10/14 08:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 47155 output: 32 thoughts: 13 Thoughts: Okay, here's my attempt at summarizing that thought process, keeping in mind the user is an expert: Tracing the Serialization Alright, so I need to understand the flow here. I'm deep in this codebase, and I've got a question nagging at me: where exactly is `luo_session_serialize` being invoked? I'm sure I've seen it used, but I need a pinpoint the calling contexts to fully grasp its role and potential impact. Understanding the points of entry will give me a better understanding of the session management strategy and how it interacts with the rest of the application. Time to fire up the search tools and trace those calls!
44/2	2026/10/14 08:46	tool	grepper	0m Args: { "Expression": "luo_session_serialize", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_core.c=220=int liveupdate_reboot(void)\n--\nkernel/liveupdate/luo_core.c-226-\nkernel/liveupdate/luo_core.c:227:\terr = luo_session_serialize();\nkernel/liveupdate/luo_core.c-228-\tif (err)\n--\nkernel/liveupdate/luo_internal.h=83=int __init luo_session_setup_incoming(u64 sessions_pa);\nkernel/liveupdate/luo_internal.h:84:int luo_session_serialize(void);\nkernel/liveupdate/luo_internal.h-85-int luo_session_deserialize(void);\n--\nkernel/liveupdate/luo_session.c-37- * 2. Serialization: When the `reboot(LINUX_REBOOT_CMD_KEXEC)` syscall is\nkernel/liveupdate/luo_session.c:38: * made, `luo_session_serialize()` is called. It iterates through all\nkernel/liveupdate/luo_session.c-39- * active sessions and writes their metadata into a memory area preserved\n--\nkernel/liveupdate/luo_session.c-55- \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)\n--\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()`)\nkernel/liveupdate/luo_session.c-64- * during reboot. On success, the write lock is held indefinitely to freeze\n--\nkernel/liveupdate/luo_session.c-79- * Lock Hierarchy:\nkernel/liveupdate/luo_session.c:80: * `luo_session_serialize_rwsem` -\u003e `luo_session_header-\u003erwsem` -\u003e `luo_session-\u003emutex`\nkernel/liveupdate/luo_session.c-81- /\n--\nkernel/liveupdate/luo_session.c-102-\nkernel/liveupdate/luo_session.c:103:static DECLARE_RWSEM(luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-104-/\n--\nkernel/liveupdate/luo_session.c=236=static int luo_session_release(struct inode inodep, struct file filep)\n--\nkernel/liveupdate/luo_session.c-240-\nkernel/liveupdate/luo_session.c:241:\tguard(rwsem_read)(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-242-\t/ If retrieved is set, it means this session is from incoming list /\n--\nkernel/liveupdate/luo_session.c=401=static long luo_session_ioctl(struct file filep, unsigned int cmd,\n--\nkernel/liveupdate/luo_session.c-435-\nkernel/liveupdate/luo_session.c:436:\tguard(rwsem_read)(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-437-\treturn op-\u003eexecute(session, \u0026ucmd);\n--\nkernel/liveupdate/luo_session.c=463=int luo_session_create(const char name, struct file filep)\n--\nkernel/liveupdate/luo_session.c-475-\nkernel/liveupdate/luo_session.c:476:\tdown_read(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-477-\terr = luo_session_insert(\u0026luo_session_global.outgoing, session);\n--\nkernel/liveupdate/luo_session.c-485-\t\tgoto err_remove;\nkernel/liveupdate/luo_session.c:486:\tup_read(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-487-\n--\nkernel/liveupdate/luo_session.c-493-\tluo_session_free(session);\nkernel/liveupdate/luo_session.c:494:\tup_read(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-495-\n--\nkernel/liveupdate/luo_session.c=499=int luo_session_retrieve(const char name, struct file **filep)\n--\nkernel/liveupdate/luo_session.c-505-\nkernel/liveupdate/luo_session.c:506:\tguard(rwsem_read)(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-507-\tguard(rwsem_read)(\u0026sh-\u003erwsem);\n--\nkernel/liveupdate/luo_session.c=585=int luo_session_deserialize(void)\n--\nkernel/liveupdate/luo_session.c-633-\nkernel/liveupdate/luo_session.c:634:int luo_session_serialize(void)\nkernel/liveupdate/luo_session.c-635-{\n--\nkernel/liveupdate/luo_session.c-640-\nkernel/liveupdate/luo_session.c:641:\tdown_write(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-642-\tdown_write(\u0026sh-\u003erwsem);\n--\nkernel/liveupdate/luo_session.c-678-\tup_write(\u0026sh-\u003erwsem);\nkernel/liveupdate/luo_session.c:679:\tup_write(\u0026luo_session_serialize_rwsem);\nkernel/liveupdate/luo_session.c-680-\n" }
45/2	2026/10/14 08:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48889 output: 28 thoughts: 53 Thoughts: Okay, let's break this down. Investigating the Reboot Sequence Right, so `liveupdate_reboot(void)` is clearly the function that's being invoked when we call `reboot(LINUX_REBOOT_CMD_KEXEC)`. That's the core trigger. Now the question is, where is `liveupdate_reboot` being called from? We need to trace back the call stack to understand the context and the potential side effects. Time to start digging through the code.
46/2	2026/10/14 08:46	tool	grepper	0m Args: { "Expression": "liveupdate_reboot", "PathPrefixes": [ "kernel/" ] } Results: { "Output": "kernel/kexec_core.c=1138=int kernel_kexec(void)\n--\nkernel/kexec_core.c-1149-\tif (!kexec_image-\u003epreserve_context) {\nkernel/kexec_core.c:1150:\t\terror = liveupdate_reboot();\nkernel/kexec_core.c-1151-\t\tif (error)\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_file.c=406=static void __luo_file_unfreeze(struct luo_file_set file_set,\n--\nkernel/liveupdate/luo_file.c-451- \nkernel/liveupdate/luo_file.c:452: Context: Called only from the liveupdate_reboot() path.\nkernel/liveupdate/luo_file.c-453- * Return: 0 on success, or a negative errno on failure.\n--\nkernel/liveupdate/luo_flb.c=570=void __init luo_flb_setup_incoming(u64 flbs_pa)\n--\nkernel/liveupdate/luo_flb.c-594- \nkernel/liveupdate/luo_flb.c:595: Context: Called from liveupdate_reboot() just before kho_finalize().\nkernel/liveupdate/luo_flb.c-596- */\n" }
47/2	2026/10/14 08:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49599 output: 34 thoughts: 73 Thoughts: Okay, let's break this down. Diving into `memfd_luo_preserve` and Its Kernel Interaction Right, so I see `memfd_luo_preserve` is triggered specifically when a userspace process makes that `ioctl` call: `ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, &arg)`. That's the entry point, the critical moment. My next move is clear. I need to understand what's happening inside that `luo_session_preserve_fd` function. Time to jump into the `kernel/liveupdate/luo_session.c` file and dissect that function. I need to trace the flow, see how it interacts with the memfd and what data is being preserved. I need to understand the implications of this action. It's time to investigate.
48/2	2026/10/14 08:46	tool	grepper	0m Args: { "Expression": "luo_session_preserve_fd", "PathPrefixes": [ "kernel/liveupdate/" ] } Results: { "Output": "kernel/liveupdate/luo_session.c=236=static int luo_session_release(struct inode inodep, struct file filep)\n--\nkernel/liveupdate/luo_session.c-263-\nkernel/liveupdate/luo_session.c:264:static int luo_session_preserve_fd(struct luo_session session,\nkernel/liveupdate/luo_session.c-265-\t\t\t\t struct luo_ucmd ucmd)\n--\nkernel/liveupdate/luo_session.c=373=static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\n--\nkernel/liveupdate/luo_session.c-375-\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:376:\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\nkernel/liveupdate/luo_session.c-377-\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\n" }
49/2	2026/10/14 08:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 50185 output: 33 thoughts: 1110 Thoughts: Analyzing the Live Update Memfd Path Okay, let's break down how this `LIVEUPDATE_SESSION_PRESERVE_FD` thing works with `memfd` files. It's clear that `luo_session_preserve_fd()` is the entry point, leading to `memfd_luo_preserve()` via `luo_file_preserve()` and `fh->ops->preserve(&args)`. And of course, `memfd_luo_unpreserve()` gets called if things are undone. For reboot scenarios via kexec, `memfd_luo_freeze()` gets involved through `luo_session_serialize()`, etc., and there's a corresponding `memfd_luo_retrieve()` upon session retrieval, followed by a final `memfd_luo_finish()`. The `shmem_freeze_seal_state` flag is crucial during freezing, preventing seal modifications after the snapshot with the `memfd_add_seals()` check and subsequent calls to `shmem_setattr()` (e.g. `chmod`) and `shmem_set_acl()`. Hold on a second, and this is important. These `shmem_set_acl` and `shmem_setattr` calls aren't just live update specific; they're the new inode operations for all tmpfs files, even without live update active! `memfd_add_seals` is triggered by `fcntl(fd, F_ADD_SEALS)` for all memfds. Now, a critical question: Can this `LIVEUPDATE_MEMFD` path be reached in standard virtualized environments like QEMU? Yes! It depends on `LIVEUPDATE`, `MEMFD_CREATE`, and `SHMEM`, all of which are core mm/kernel features. No specialized hardware dependencies here. Let's run down the checklist: - Non-kernel modifications? No, we're dealing with shmem, memfd, liveupdate code. - Unreachable hardware? Nope, just shmem and memfd. - Unreachable execution paths (like PCI hot-unplug)? No, no such exclusions. - And crucially, can the code execute in QEMU/GCE? Yes! Given all that, the conclusion is clear: `WorthFuzzing = true`! Let's carefully verify the config requirements. We need `LIVEUPDATE_MEMFD`, which in turn needs `LIVEUPDATE`, `MEMFD_CREATE`, and `SHMEM`. `LIVEUPDATE` needs `KEXEC_HANDOVER`. Let's double-check the Kconfig dependencies. Specifically, does amd64 support `ARCH_SUPPORTS_KEXEC_HANDOVER`? Time to check the kernel source.
50/2	2026/10/14 08:47	tool	grepper	0m Args: { "Expression": "ARCH_SUPPORTS_KEXEC_HANDOVER", "PathPrefixes": [ "arch/" ] } Results: { "Output": "arch/arm64/Kconfig=1654=config ARCH_DEFAULT_KEXEC_IMAGE_VERIFY_SIG\n--\narch/arm64/Kconfig-1656-\narch/arm64/Kconfig:1657:config ARCH_SUPPORTS_KEXEC_HANDOVER\narch/arm64/Kconfig-1658-\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" }
51/2	2026/10/14 08:47	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 52127 output: 34 thoughts: 171 Thoughts: Kernel Configuration Exploration Okay, so I'm digging into these kernel configurations related to kexec and trying to understand their implications for our x86_64 architecture, specifically AMD64. First, `ARCH_SUPPORTS_KEXEC_HANDOVER` is defined as a boolean (`def_bool`) and it's enabled for X86_64, which is expected. The target is AMD64, so that makes sense. Now, what about `ARCH_SUPPORTS_KEXEC_FILE`? Let me quickly verify, yep, it's also enabled on X86! Good. Consistent so far. Next up, `KEXEC_HANDOVER_ENABLE_DEFAULT`. I know that if this config is enabled, it means that the `kho_enable` variable will be set to true by default. That's pretty significant, as the system would not require `kho=on` on the kernel command line. That could save a user some trouble. Finally, I'm curious about `CONFIG_TMPFS_POSIX_ACL`. I'm going to quickly check in `fs/Kconfig` or maybe even `mm/Kconfig` to see where that is defined and understand the context.
52/2	2026/10/14 08:47	tool	grepper	0m Args: { "Expression": "TMPFS_POSIX_ACL", "PathPrefixes": [ "fs/", "mm/" ] } Results: { "Output": "fs/Kconfig=167=config TMPFS\n--\nfs/Kconfig-180-\nfs/Kconfig:181:config TMPFS_POSIX_ACL\nfs/Kconfig-182-\tbool \"Tmpfs POSIX Access Control Lists\"\n--\nmm/shmem.c=1316=static int shmem_setattr(struct mnt_idmap idmap,\n--\nmm/shmem.c-1395-\nmm/shmem.c:1396:#ifdef CONFIG_TMPFS_POSIX_ACL\nmm/shmem.c-1397-static int shmem_set_acl(struct mnt_idmap idmap, struct dentry dentry,\n--\nmm/shmem.c=4936=static int shmem_fill_super(struct super_block sb, struct fs_context *fc)\n--\nmm/shmem.c-5025-#endif\nmm/shmem.c:5026:#ifdef CONFIG_TMPFS_POSIX_ACL\nmm/shmem.c-5027-\tsb-\u003es_flags \|= SB_POSIXACL;\n--\nmm/shmem.c=5171=static const struct inode_operations shmem_inode_operations = {\n--\nmm/shmem.c-5175-\t.listxattr\t= shmem_listxattr,\nmm/shmem.c:5176:#ifdef CONFIG_TMPFS_POSIX_ACL\nmm/shmem.c-5177-\t.set_acl\t= shmem_set_acl,\n--\nmm/shmem.c=5184=static const struct inode_operations shmem_dir_inode_operations = {\n--\nmm/shmem.c-5203-#endif\nmm/shmem.c:5204:#ifdef CONFIG_TMPFS_POSIX_ACL\nmm/shmem.c-5205-\t.setattr\t= shmem_setattr,\n--\nmm/shmem.c=5210=static const struct inode_operations shmem_special_inode_operations = {\n--\nmm/shmem.c-5214-#endif\nmm/shmem.c:5215:#ifdef CONFIG_TMPFS_POSIX_ACL\nmm/shmem.c-5216-\t.setattr\t= shmem_setattr,\n" }
53/2	2026/10/14 08:47	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 53173 output: 32 thoughts: 19 Thoughts: Here's my thought process, as requested: Navigating the Filesystem Configuration for POSIX ACLs in TMPFS Okay, so I need to understand how `TMPFS_POSIX_ACL` is handled in the kernel's filesystem configuration. My immediate instinct is to check `fs/Kconfig`. That's where I expect to find the relevant configuration options and dependencies. I'm looking for the definitions related to this specific feature, to see how it's enabled, disabled, and perhaps any related configurations that might affect its behavior. I need a clear understanding of the configuration context around this to proceed with whatever I'm working on, whether it be debugging, understanding a new patch, or something else. Let's dig in.
54/2	2026/10/14 08:47	tool	read-file	0m Args: { "File": "fs/Kconfig", "FirstLine": 175, "LineCount": 25 } Results: { "Contents": " 175:\t\t created on your hard drive. The files live in memory and swap\n 176:\t\t space. If you unmount a tmpfs instance, everything stored therein is\n 177:\t\t lost.\n 178:\t\n 179:\t\t See \u003cfile:Documentation/filesystems/tmpfs.rst\u003e for details.\n 180:\t\n 181:\tconfig TMPFS_POSIX_ACL\n 182:\t\tbool \"Tmpfs POSIX Access Control Lists\"\n 183:\t\tdepends on TMPFS\n 184:\t\tselect TMPFS_XATTR\n 185:\t\tselect FS_POSIX_ACL\n 186:\t\thelp\n 187:\t\t POSIX Access Control Lists (ACLs) support additional access rights\n 188:\t\t for users and groups beyond the standard owner/group/world scheme,\n 189:\t\t and this option selects support for ACLs specifically for tmpfs\n 190:\t\t filesystems.\n 191:\t\n 192:\t\t If you've selected TMPFS, it's possible that you'll also need\n 193:\t\t this option as there are a number of Linux distros that require\n 194:\t\t POSIX ACL support under /dev for certain features to work properly.\n 195:\t\t For example, some distros need this feature for ALSA-related /dev\n 196:\t\t files for sound to work properly. In short, if you're not sure,\n 197:\t\t say Y.\n 198:\t\n 199:\tconfig TMPFS_XATTR\n" }
55/2	2026/10/14 08:47	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 53792 output: 32 thoughts: 188 Thoughts: Okay, let's get down to brass tacks. Configuration Audit: Live Update and Memory File Systems Right, I need to methodically verify the configuration options related to live update and memory file systems. First, I'll go through the relevant configs: `CONFIG_TMPFS_POSIX_ACL`, `CONFIG_LIVEUPDATE_MEMFD`, `CONFIG_LIVEUPDATE`, `CONFIG_KEXEC_HANDOVER`, `CONFIG_MEMFD_CREATE`, `CONFIG_SHMEM`, and `CONFIG_TMPFS`. Now, I'm thinking about the dependencies. `LIVEUPDATE_MEMFD` obviously relies on `LIVEUPDATE`, `MEMFD_CREATE`, and `SHMEM`. `LIVEUPDATE` depends on `KEXEC_HANDOVER`, which is important for the whole live update flow. And then there's `TMPFS_POSIX_ACL`, that's got to be working correctly for the file systems. Hang on... I need to consider `KEXEC_HANDOVER_ENABLE_DEFAULT`. It enables KHO by default, so its state needs to be taken into account. I need to figure out its relationship with the rest of this system. Just to be thorough, I'm also going to examine `mm/memfd_luo.c` to make sure I haven't missed any other `#ifdef` directives or configuration variables that might be relevant to live updates or memory file descriptors. Gotta cover all the bases.
56/2	2026/10/14 08:47	tool	grepper	0m Error: no matches Args: { "Expression": "#if", "PathPrefixes": [ "mm/memfd_luo.c" ] } Results: { "error": "no matches" }
57/2	2026/10/14 08:47	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 54332 output: 30 thoughts: 925 Thoughts: Analyzing the Patch for Symbol Coverage Okay, first thing's first: there's no `#if` in `mm/memfd_luo.c`, so we don't need to worry about conditional compilation here. Now, let's break down the changes and figure out which functions are relevant for symbol coverage. In `mm/memfd.c`, `memfd_add_seals` has been modified. It's checking `shmem_seal_state_frozen(inode)` now. Moving on to `mm/shmem.c`, `shmem_setattr` is also modified, again checking `shmem_seal_state_frozen(inode)` when handling mode attributes. There's also a new function, `shmem_set_acl`, which similarly checks for a frozen state before calling `simple_set_acl`. `mm/memfd_luo.c` is where things get interesting. We have a suite of new static functions: `memfd_luo_record_exec_mode`, `memfd_luo_restore_exec_mode`, then a bunch of callbacks like `memfd_luo_preserve`, `memfd_luo_freeze`, `memfd_luo_unfreeze`, `memfd_luo_unpreserve`, `memfd_luo_release_ser`, `memfd_luo_finish`, `memfd_luo_retrieve`, `memfd_luo_can_preserve`, and `memfd_luo_can_preserve_v2`. Finally, there's `memfd_luo_init`, which is an initcall. Hold on... are these static functions actually symbols in the vmlinux? Yeah, they can be, as long as they're not inlined by the compiler. Okay, let's make sure we're following the section guidelines... The guideline specifically mentions static inline functions lacking distinct symbols; that doesn't seem to apply here. But, we have to target specific feature logic and entrypoints, and avoid ubiquitous lifecycle functions. We don't want to dilute our fuzzing efforts. Alright, let's go through the candidates one by one: First, `memfd_add_seals`. Is this ubiquitous? No, it's pretty specific to memfd sealing; it's called via `fcntl(fd, F_ADD_SEALS, ...)`. Hmm, is `memfd_add_seals` exported or non-static? Need to check the code...
58/2	2026/10/14 08:47	tool	grepper	0m Args: { "Expression": "memfd_add_seals", "PathPrefixes": [ "mm/" ] } Results: { "Output": "mm/memfd.c=210=static unsigned int memfd_file_seals_ptr(struct file file)\n--\nmm/memfd.c-229-\nmm/memfd.c:230:int memfd_add_seals(struct file file, unsigned int seals)\nmm/memfd.c-231-{\n--\nmm/memfd.c=325=long memfd_fcntl(struct file file, unsigned int cmd, unsigned int arg)\n--\nmm/memfd.c-330-\tcase F_ADD_SEALS:\nmm/memfd.c:331:\t\terror = memfd_add_seals(file, arg);\nmm/memfd.c-332-\t\tbreak;\n--\nmm/memfd_luo.c=371=static int memfd_luo_freeze(struct liveupdate_file_op_args args)\n--\nmm/memfd_luo.c-384-\t and seals can differ from the values recorded by preserve(). Take the\nmm/memfd_luo.c:385:\t * final snapshot under the inode lock shared with memfd_add_seals(),\nmm/memfd_luo.c-386-\t * shmem_setattr(), and shmem_set_acl(), then freeze those state fields\n--\nmm/memfd_luo.c=613=static int memfd_luo_retrieve(struct liveupdate_file_op_args args)\n--\nmm/memfd_luo.c-655-\t F_SEAL_EXEC freezes each execute bit, and the W^X rule in\nmm/memfd_luo.c:656:\t * memfd_add_seals() looks at the mode when deciding whether to imply the\nmm/memfd_luo.c-657-\t * write seals. The fresh anonymous inode has not been published, so no\n--\nmm/memfd_luo.c-663-\nmm/memfd_luo.c:664:\terr = memfd_add_seals(file, ser-\u003eseals);\nmm/memfd_luo.c-665-\tif (err) {\n" }
59/2	2026/10/14 08:47	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56388 output: 287 thoughts: 3646 Thoughts: Analysis of Live Update Fuzzing Targets Okay, let's break this down. We're looking at a patch that extends memfd and tmpfs live update capabilities, specifically around preserving and freezing execute permissions and seal states during kexec live updates. The changes impact synchronization and access control, so fuzzing is definitely warranted. We need to identify the key functions to target and the necessary configuration options. First, `memfd_add_seals` has been modified. It's not a static symbol, and it's called directly by `memfd_luo_retrieve` and `fcntl(F_ADD_SEALS)`, making it a prime candidate. We also see modifications to `shmem_set_acl`, a function specifically for ACL operations on tmpfs, and `shmem_setattr` which changes the attributes of files within tmpfs. However, `shmem_setattr` appears to be a very general function called in numerous scenarios. We should avoid "ubiquitous lifecycle hot-paths" like that to avoid diluting fuzzing. `shmem_set_acl` however is a solid target, being specific to the introduced ACL handling. Then there are the functions in `mm/memfd_luo.c`: `memfd_luo_preserve`, `memfd_luo_freeze`, `memfd_luo_unfreeze`, `memfd_luo_unpreserve`, `memfd_luo_retrieve`, `memfd_luo_finish`, and `memfd_luo_can_preserve`. These are all part of the Live Update Orchestrator (LUO) and are definitely worth targeting, since they are core to the new functionality. Because they are called through function pointers, the compiler will not inline them away, meaning they are guaranteed symbols. The functions modified by the patch are: In `mm/memfd.c`: `memfd_add_seals`. In `mm/memfd_luo.c`: `memfd_luo_preserve`, `memfd_luo_freeze`, `memfd_luo_unfreeze`, `memfd_luo_unpreserve`, `memfd_luo_retrieve`, `memfd_luo_finish`, `memfd_luo_can_preserve`, `memfd_luo_can_preserve_v2`, `memfd_luo_release_ser`. In `mm/shmem.c`: `shmem_set_acl`, `shmem_setattr`. So, the symbols to target for fuzzing are: - `memfd_luo_preserve` - `memfd_luo_freeze` - `memfd_luo_unfreeze` - `memfd_luo_retrieve` - `memfd_luo_finish` - `memfd_luo_can_preserve` - `memfd_add_seals` - `shmem_set_acl` We need to make sure the relevant configs are enabled. Let's look: - `LIVEUPDATE_MEMFD` - This compiles `memfd_luo.c` which includes the new logic. - `LIVEUPDATE` - This is required by `LIVEUPDATE_MEMFD`. - `KEXEC_HANDOVER` - This enables KEXEC and is a dependency of `LIVEUPDATE`. - `KEXEC_HANDOVER_ENABLE_DEFAULT` - Enables KEXEC automatically if KEXEC_HANDOVER is enabled. - `TMPFS_POSIX_ACL` - This is required for ACL operations on tmpfs which enables `shmem_set_acl`. - `MEMFD_CREATE` - This is required to create `memfd` files. - `TMPFS` - And finally the base for TMPFS functionality. Therefore the configurations to include are: - `LIVEUPDATE_MEMFD` - `LIVEUPDATE` - `KEXEC_HANDOVER` - `KEXEC_HANDOVER_ENABLE_DEFAULT` - `TMPFS_POSIX_ACL` - `MEMFD_CREATE` - `TMPFS`
60/2	2026/10/14 08:48	tool	set-results	0m Args: { "EnableConfigs": [ "LIVEUPDATE_MEMFD", "LIVEUPDATE", "KEXEC_HANDOVER", "KEXEC_HANDOVER_ENABLE_DEFAULT", "TMPFS_POSIX_ACL", "MEMFD_CREATE", "TMPFS" ], "FocusSymbols": [ "memfd_luo_preserve", "memfd_luo_freeze", "memfd_luo_unfreeze", "memfd_luo_retrieve", "memfd_luo_finish", "memfd_luo_can_preserve", "memfd_add_seals", "shmem_set_acl" ], "Reasoning": "The patch modifies the Live Update Orchestrator (LUO) support for memfd and shmem/tmpfs. It introduces logic to preserve user/group/other execute permission bits and seal state across kexec live update transitions. It adds seal state freezing checks in memfd_add_seals() and shmem_setattr(), introduces shmem_set_acl() to prevent ACL modifications from diverging execution permissions after snapshotting, and implements unfreeze/error rollback handling in memfd_luo.c. These changes touch reachable core memory management and file system logic accessible from userspace.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "LIVEUPDATE_MEMFD", "LIVEUPDATE", "KEXEC_HANDOVER", "KEXEC_HANDOVER_ENABLE_DEFAULT", "TMPFS_POSIX_ACL", "MEMFD_CREATE", "TMPFS" ], "FocusSymbols": [ "memfd_luo_preserve", "memfd_luo_freeze", "memfd_luo_unfreeze", "memfd_luo_retrieve", "memfd_luo_finish", "memfd_luo_can_preserve", "memfd_add_seals", "shmem_set_acl" ], "Reasoning": "The patch modifies the Live Update Orchestrator (LUO) support for memfd and shmem/tmpfs. It introduces logic to preserve user/group/other execute permission bits and seal state across kexec live update transitions. It adds seal state freezing checks in memfd_add_seals() and shmem_setattr(), introduces shmem_set_acl() to prevent ACL modifications from diverging execution permissions after snapshotting, and implements unfreeze/error rollback handling in memfd_luo.c. These changes touch reachable core memory management and file system logic accessible from userspace.", "WorthFuzzing": true }
61/1	2026/10/14 08:48	action	If	1m Args: { "WorthFuzzing": true } Results: null
62/2	2026/10/14 08:48	agent	kmsan-evaluator	1m Model: core Args: null Results: { "KMSANReasoning": "The patch series updates memfd Live Update Orchestration (LUO) and shmem to preserve exact execute permission bits (user/group/other) across kexec reboots (supporting F_SEAL_EXEC), and freezes the seal/mode state during liveupdate to prevent divergence.\n\nAnalysis with respect to memory sanitizers:\n1. No uninitialized memory or info-leak risks:\n - The serialization record `struct memfd_luo_ser` is allocated via `kho_alloc_preserve()`, which internally uses `folio_alloc()` with `__GFP_ZERO`, ensuring all fields and padding are zero-initialized.\n - All newly added local variables (`flags`, `mode`, `folios_ser`) are explicitly initialized before use.\n - The serialized structure is exchanged internally between kernels during kexec handover (KHO) and is not copied to userspace. No data structures or padding are exposed to userspace via `copy_to_user`, ioctls, or netlink.\n2. KASAN/LOCKDEP applicability:\n - Any potential issues introduced by this patch revolve around concurrency/locking (`shmem_seal_state_frozen` lock discipline, inode lock serialization), file reference handling (`fput`), or folio lifetime management (`memfd_luo_discard_folios`), which are covered by standard KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nTherefore, this patch series does not introduce uninitialized memory read risks or kernel-to-user info-leaks, and a dedicated KMSAN session is not required.", "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 b3d3d95b3632992db943db5e3203c4584c36d58d Author: syz-cluster <triage@syzkaller.com> Date: Wed Oct 14 08:43:46 2026 +0000 syz-cluster: applied patch under review diff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h index 08b10fea2afc8..f773dd95401d2 100644 --- a/include/linux/kho/abi/memfd.h +++ b/include/linux/kho/abi/memfd.h @@ -87,7 +87,29 @@ struct memfd_luo_ser { struct kho_vmalloc folios; } __packed; +/* + * The execute permission bits are packed in user/group/other order. A record + * with none of these flags set is restored without execute permissions, which + * is also the safe interpretation for records written before these flags + * existed. + / +#define MEMFD_LUO_FL_EXEC_USR BIT(0) +#define MEMFD_LUO_FL_EXEC_GRP BIT(1) +#define MEMFD_LUO_FL_EXEC_OTH BIT(2) +#define MEMFD_LUO_FL_EXEC_MASK (MEMFD_LUO_FL_EXEC_USR \| \ + MEMFD_LUO_FL_EXEC_GRP \| \ + MEMFD_LUO_FL_EXEC_OTH) +#define MEMFD_LUO_ALL_FLAGS MEMFD_LUO_FL_EXEC_MASK + / The compatibility string for memfd file handler / -#define MEMFD_LUO_FH_COMPATIBLE "memfd-v2" +#define MEMFD_LUO_FH_COMPATIBLE "memfd-v3" +/ + * Records written before the execute-bit flags existed. They carry no flag + * bits and are restored without execute permissions: the flags cannot tell + * "the execute bits were clear" and "the writer did not know about the flags" + * apart, and restoring without them is the safe reading. The current kernel + * still accepts these records but never writes them. + / +#define MEMFD_LUO_FH_COMPATIBLE_V2 "memfd-v2" #endif / _LINUX_KHO_ABI_MEMFD_H / diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index e729b9b0e38d4..40e1ce87c30e0 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -32,6 +32,12 @@ struct swap_iocb; isn't directly visible to userspace. / #define SHMEM_F_MAPPING_FROZEN BIT(2) +/ + * Disallow changes to the seal set and execute bits captured by the final LUO + * snapshot. This is set only for the reboot transition and is cleared if the + * transition is rolled back. + / +#define SHMEM_F_SEAL_STATE_FROZEN BIT(3) struct shmem_inode_info { spinlock_t lock; @@ -208,6 +214,20 @@ static inline void shmem_freeze(struct inode inode, bool freeze) SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN; } +/* Must be called with inode lock taken exclusive. / +static inline void shmem_freeze_seal_state(struct inode inode, bool freeze) +{ + if (freeze) + SHMEM_I(inode)->flags \|= SHMEM_F_SEAL_STATE_FROZEN; + else + SHMEM_I(inode)->flags &= ~SHMEM_F_SEAL_STATE_FROZEN; +} + +static inline bool shmem_seal_state_frozen(struct inode inode) +{ + return SHMEM_I(inode)->flags & SHMEM_F_SEAL_STATE_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/memfd.c b/mm/memfd.c index abe13b291ddc8..578ac31ed1a9e 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -278,6 +278,12 @@ int memfd_add_seals(struct file file, unsigned int seals) goto unlock; } + / LUO has taken its final snapshot; do not let the seal set diverge. / + if (shmem_file(file) && shmem_seal_state_frozen(inode)) { + error = -EPERM; + goto unlock; + } + if (file_seals & F_SEAL_SEAL) { error = -EPERM; goto unlock; diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c index 59de210bee5f9..f1f07d90f73d1 100644 --- a/mm/memfd_luo.c +++ b/mm/memfd_luo.c @@ -50,6 +50,16 @@ * memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property * is maintained. * + * Execute Permission Bits + * The user, group, and other execute bits are preserved individually. This + * is required to faithfully restore the state protected by ``F_SEAL_EXEC``. + * + * .. note:: + * A record written by an older kernel (``memfd-v2``) does not carry the + * execute bits. It is restored without execute permissions, which is the + * safe reading: an executable memfd preserved by such a kernel comes back + * non-executable, and the next update records the exact state. + * * Seals * File seals set on the memfd are preserved and re-applied on restore. * Only seals known to this LUO version (see ``MEMFD_LUO_ALL_SEALS``) may @@ -84,6 +94,35 @@ #include "internal.h" +static void memfd_luo_record_exec_mode(struct memfd_luo_ser ser, umode_t mode) +{ + u32 flags = 0; + + if (mode & 0100) + flags \|= MEMFD_LUO_FL_EXEC_USR; + if (mode & 0010) + flags \|= MEMFD_LUO_FL_EXEC_GRP; + if (mode & 0001) + flags \|= MEMFD_LUO_FL_EXEC_OTH; + + ser->flags &= ~MEMFD_LUO_FL_EXEC_MASK; + ser->flags \|= flags; +} + +static umode_t memfd_luo_restore_exec_mode(u32 flags) +{ + umode_t mode = 0; + + if (flags & MEMFD_LUO_FL_EXEC_USR) + mode \|= 0100; + if (flags & MEMFD_LUO_FL_EXEC_GRP) + mode \|= 0010; + if (flags & MEMFD_LUO_FL_EXEC_OTH) + mode \|= 0001; + + return mode; +} + static int memfd_luo_preserve_folios(struct file file, struct kho_vmalloc kho_vmalloc, struct memfd_luo_folio_ser out_folios_ser, @@ -300,6 +339,14 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args args) ser->size = inode_size; ser->seals = seals; + /* + * F_SEAL_EXEC freezes each execute permission bit independently, so + * preserve the complete user/group/other execute mask. A record with no + * execute flags is restored without execute permissions, which is also + * the safe interpretation for records written before these flags existed. + / + memfd_luo_record_exec_mode(ser, inode->i_mode); + err = memfd_luo_preserve_folios(args->file, &ser->folios, &folios_ser, &nr_folios); if (err) @@ -323,7 +370,9 @@ static int memfd_luo_preserve(struct liveupdate_file_op_args args) static int memfd_luo_freeze(struct liveupdate_file_op_args args) { + struct inode inode = file_inode(args->file); struct memfd_luo_ser ser; + int seals; if (WARN_ON_ONCE(!args->serialized_data)) return -EINVAL; @@ -331,14 +380,47 @@ static int memfd_luo_freeze(struct liveupdate_file_op_args args) ser = phys_to_virt(args->serialized_data); /* - * The pos might have changed since prepare. Everything else stays the - * same. + * The file is still usable between preserve() and freeze(), so its mode + * and seals can differ from the values recorded by preserve(). Take the + * final snapshot under the inode lock shared with memfd_add_seals(), + * shmem_setattr(), and shmem_set_acl(), then freeze those state fields + * before dropping the lock. This closes the window in which a later + * chmod(), ACL update, or F_ADD_SEALS could otherwise diverge from the + * state handed to the next kernel. / + inode_lock(inode); + + seals = memfd_get_seals(args->file); + if (seals < 0) { + inode_unlock(inode); + return seals; + } + + / The file must not have gained seals that this version does not know. / + if (seals & ~MEMFD_LUO_ALL_SEALS) { + inode_unlock(inode); + return -EOPNOTSUPP; + } + + memfd_luo_record_exec_mode(ser, inode->i_mode); + ser->seals = seals; ser->pos = args->file->f_pos; + shmem_freeze_seal_state(inode, true); + + inode_unlock(inode); return 0; } +static void memfd_luo_unfreeze(struct liveupdate_file_op_args args) +{ + struct inode inode = file_inode(args->file); + + inode_lock(inode); + shmem_freeze_seal_state(inode, false); + inode_unlock(inode); +} + static void memfd_luo_unpreserve(struct liveupdate_file_op_args args) { struct inode inode = file_inode(args->file); @@ -348,6 +430,7 @@ static void memfd_luo_unpreserve(struct liveupdate_file_op_args args) return; inode_lock(inode); + shmem_freeze_seal_state(inode, false); shmem_freeze(inode, false); ser = phys_to_virt(args->serialized_data); @@ -384,9 +467,31 @@ static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser folios_se } } -static void memfd_luo_finish(struct liveupdate_file_op_args args) +/* + * Release a preserved record: return its folios to the page allocator and free + * the record itself. Only valid for records whose folios were never handed to + * a file -- handing a folio to a file consumes its last reference, and + * memfd_luo_discard_folios() would release it a second time. + / +static void memfd_luo_release_ser(struct memfd_luo_ser ser) { struct memfd_luo_folio_ser folios_ser; + + if (ser->nr_folios) { + folios_ser = kho_restore_vmalloc(&ser->folios); + if (!folios_ser) + goto out; + + memfd_luo_discard_folios(folios_ser, ser->nr_folios); + vfree(folios_ser); + } + +out: + kho_restore_free(ser); +} + +static void memfd_luo_finish(struct liveupdate_file_op_args args) +{ struct memfd_luo_ser ser; / @@ -401,17 +506,7 @@ static void memfd_luo_finish(struct liveupdate_file_op_args args) if (!ser) return; - if (ser->nr_folios) { - folios_ser = kho_restore_vmalloc(&ser->folios); - if (!folios_ser) - goto out; - - memfd_luo_discard_folios(folios_ser, ser->nr_folios); - vfree(folios_ser); - } - -out: - kho_restore_free(ser); + memfd_luo_release_ser(ser); } static int memfd_luo_retrieve_folios(struct file file, @@ -517,32 +612,55 @@ static int memfd_luo_retrieve_folios(struct file file, static int memfd_luo_retrieve(struct liveupdate_file_op_args args) { - struct memfd_luo_folio_ser folios_ser; + struct memfd_luo_folio_ser folios_ser = NULL; struct memfd_luo_ser ser; struct file file; + umode_t exec_mode; int err; ser = phys_to_virt(args->serialized_data); if (!ser) return -EINVAL; - /* Make sure the file only has seals supported by this version. / - if (ser->seals & ~MEMFD_LUO_ALL_SEALS) { + / Make sure the record only contains state supported by this version. / + if ((ser->seals & ~MEMFD_LUO_ALL_SEALS) \|\| + (ser->flags & ~MEMFD_LUO_ALL_FLAGS)) { err = -EOPNOTSUPP; - goto free_ser; + goto release_ser; } / - * The seals are preserved. Allow sealing here so they can be added - * later. + * Restore the folio array before allocating the file. Once this succeeds, + * every later error path can release the preserved folios directly instead + * of allocating memory again while already handling a failure. / + if (ser->nr_folios) { + folios_ser = kho_restore_vmalloc(&ser->folios); + if (!folios_ser) { + / kho_restore_vmalloc() is not safe to retry after failure. / + err = -EINVAL; + goto free_ser; + } + } + file = memfd_alloc_file("", MFD_ALLOW_SEALING); if (IS_ERR(file)) { pr_err("failed to setup file: %pe\n", file); err = PTR_ERR(file); - goto free_ser; + goto discard_folios; } + / + * Reproduce the exact execute mask before the seals are re-applied: + * F_SEAL_EXEC freezes each execute bit, and the W^X rule in + * memfd_add_seals() looks at the mode when deciding whether to imply the + * write seals. The fresh anonymous inode has not been published, so no + * other thread can observe this intermediate state. + / + exec_mode = memfd_luo_restore_exec_mode(ser->flags); + file->f_inode->i_mode &= ~0111; + file->f_inode->i_mode \|= exec_mode; + err = memfd_add_seals(file, ser->seals); if (err) { pr_err("failed to add seals: %pe\n", ERR_PTR(err)); @@ -552,15 +670,12 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args args) vfs_setpos(file, ser->pos, MAX_LFS_FILESIZE); i_size_write(file_inode(file), ser->size); - if (ser->nr_folios) { - folios_ser = kho_restore_vmalloc(&ser->folios); - if (!folios_ser) { - err = -EINVAL; - goto put_file; - } - - err = memfd_luo_retrieve_folios(file, folios_ser, ser->nr_folios); + if (folios_ser) { + /* retrieve_folios() consumes every preserved data folio. / + err = memfd_luo_retrieve_folios(file, folios_ser, + ser->nr_folios); vfree(folios_ser); + folios_ser = NULL; if (err) goto put_file; } @@ -572,9 +687,18 @@ static int memfd_luo_retrieve(struct liveupdate_file_op_args args) put_file: fput(file); +discard_folios: + if (folios_ser) { + memfd_luo_discard_folios(folios_ser, ser->nr_folios); + vfree(folios_ser); + } free_ser: kho_restore_free(ser); return err; + +release_ser: + memfd_luo_release_ser(ser); + return err; } static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler, @@ -582,7 +706,12 @@ static bool memfd_luo_can_preserve(struct liveupdate_file_handler handler, { struct inode inode = file_inode(file); - return shmem_file(file) && !inode->i_nlink; + / + * shmem_kernel_file_setup() marks kernel-private files S_PRIVATE. In + * particular, SysV SHM updates SHMEM_I(inode)->flags under its IPC lock, + * which does not serialize with the inode lock used by LUO. + / + return shmem_file(file) && !IS_PRIVATE(inode) && !inode->i_nlink; } static unsigned long memfd_luo_get_id(struct file file) @@ -592,6 +721,7 @@ static unsigned long memfd_luo_get_id(struct file file) static const struct liveupdate_file_ops memfd_luo_file_ops = { .freeze = memfd_luo_freeze, + .unfreeze = memfd_luo_unfreeze, .finish = memfd_luo_finish, .retrieve = memfd_luo_retrieve, .preserve = memfd_luo_preserve, @@ -606,15 +736,62 @@ static struct liveupdate_file_handler memfd_luo_handler = { .compatible = MEMFD_LUO_FH_COMPATIBLE, }; +/ + * Reads records written before the execute-bit flags existed. Those have no + * flag bits and are restored without execute permissions (see the note on + * old records in the DOC section above). can_preserve() never claims a file, + * so an outgoing preservation is always written by the handler above and + * never as "memfd-v2". + / +static bool memfd_luo_can_preserve_v2(struct liveupdate_file_handler handler, + struct file file) +{ + return false; +} + +static const struct liveupdate_file_ops memfd_luo_file_ops_v2 = { + .freeze = memfd_luo_freeze, + .unfreeze = memfd_luo_unfreeze, + .finish = memfd_luo_finish, + .retrieve = memfd_luo_retrieve, + .preserve = memfd_luo_preserve, + .unpreserve = memfd_luo_unpreserve, + .can_preserve = memfd_luo_can_preserve_v2, + .get_id = memfd_luo_get_id, + .owner = THIS_MODULE, +}; + +static struct liveupdate_file_handler memfd_luo_handler_v2 = { + .ops = &memfd_luo_file_ops_v2, + .compatible = MEMFD_LUO_FH_COMPATIBLE_V2, +}; + static int __init memfd_luo_init(void) { - int err = liveupdate_register_file_handler(&memfd_luo_handler); + int err; + + err = liveupdate_register_file_handler(&memfd_luo_handler); + if (err) { + if (err != -EOPNOTSUPP) { + pr_err("Could not register luo filesystem handler: %pe\n", + ERR_PTR(err)); + return err; + } - if (err && err != -EOPNOTSUPP) { - pr_err("Could not register luo filesystem handler: %pe\n", - ERR_PTR(err)); + return 0; + } + + err = liveupdate_register_file_handler(&memfd_luo_handler_v2); + if (err) { + liveupdate_unregister_file_handler(&memfd_luo_handler); - return err; + if (err != -EOPNOTSUPP) { + pr_err("Could not register the memfd-v2 record reader: %pe\n", + ERR_PTR(err)); + return err; + } + + return 0; } return 0; diff --git a/mm/shmem.c b/mm/shmem.c index b51f83c970bb3..55f4dbd429eb9 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1326,11 +1326,10 @@ static int shmem_setattr(struct mnt_idmap idmap, if (error) return error; - if ((info->seals & F_SEAL_EXEC) && (attr->ia_valid & ATTR_MODE)) { - if ((inode->i_mode ^ attr->ia_mode) & 0111) { - return -EPERM; - } - } + if ((attr->ia_valid & ATTR_MODE) && + ((info->seals & F_SEAL_EXEC) \|\| shmem_seal_state_frozen(inode)) && + ((inode->i_mode ^ attr->ia_mode) & 0111)) + return -EPERM; if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) { loff_t oldsize = inode->i_size; @@ -1394,6 +1393,24 @@ static int shmem_setattr(struct mnt_idmap idmap, return error; } +#ifdef CONFIG_TMPFS_POSIX_ACL +static int shmem_set_acl(struct mnt_idmap idmap, struct dentry dentry, + struct posix_acl acl, int type) +{ + struct inode inode = d_inode(dentry); + + / + * An access ACL can rewrite the inode's execute bits without going + * through shmem_setattr(). Once LUO has captured its final seal/mode + * snapshot, reject that alternate mutation path as well. + / + if (type == ACL_TYPE_ACCESS && shmem_seal_state_frozen(inode)) + return -EPERM; + + return simple_set_acl(idmap, dentry, acl, type); +} +#endif + static void shmem_evict_inode(struct inode inode) { struct shmem_inode_info info = SHMEM_I(inode); @@ -5156,7 +5173,9 @@ static const struct inode_operations shmem_inode_operations = { .setattr = shmem_setattr, #ifdef CONFIG_TMPFS_XATTR .listxattr = shmem_listxattr, - .set_acl = simple_set_acl, +#ifdef CONFIG_TMPFS_POSIX_ACL + .set_acl = shmem_set_acl, +#endif .fileattr_get = shmem_fileattr_get, .fileattr_set = shmem_fileattr_set, #endif @@ -5184,7 +5203,7 @@ static const struct inode_operations shmem_dir_inode_operations = { #endif #ifdef CONFIG_TMPFS_POSIX_ACL .setattr = shmem_setattr, - .set_acl = simple_set_acl, + .set_acl = shmem_set_acl, #endif }; @@ -5195,7 +5214,7 @@ static const struct inode_operations shmem_special_inode_operations = { #endif #ifdef CONFIG_TMPFS_POSIX_ACL .setattr = shmem_setattr, - .set_acl = simple_set_acl, + .set_acl = shmem_set_acl, #endif }; diff --git a/tools/testing/selftests/liveupdate/luo_kexec_simple.c b/tools/testing/selftests/liveupdate/luo_kexec_simple.c index d7ac1f3dc4cbc..30836043f894e 100644 --- a/tools/testing/selftests/liveupdate/luo_kexec_simple.c +++ b/tools/testing/selftests/liveupdate/luo_kexec_simple.c @@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0-only +#define _GNU_SOURCE / * Copyright (c) 2025, Google LLC. @@ -8,16 +9,211 @@ * across a single kexec reboot. / +#include <fcntl.h> +#include <sys/ioctl.h> +#include <sys/mman.h> +#include <sys/stat.h> +#include <unistd.h> + +#include <linux/memfd.h> + #include "luo_test_utils.h" +#ifndef F_SEAL_SHRINK +#define F_SEAL_SHRINK 0x0002 +#endif +#ifndef F_SEAL_GROW +#define F_SEAL_GROW 0x0004 +#endif +#ifndef F_SEAL_WRITE +#define F_SEAL_WRITE 0x0008 +#endif +#ifndef F_SEAL_FUTURE_WRITE +#define F_SEAL_FUTURE_WRITE 0x0010 +#endif +#ifndef F_SEAL_EXEC +#define F_SEAL_EXEC 0x0020 +#endif +#ifndef MFD_NOEXEC_SEAL +#define MFD_NOEXEC_SEAL 0x0008U +#endif + +/ + * F_SEAL_EXEC implies the write seals when the memfd has execute bits (the + * W^X rule in memfd_add_seals()), so a memfd that was chmod()ed to 0700 + * before F_SEAL_EXEC was added ends up with exactly this seal set. + / +#define F_WX_SEALS (F_SEAL_EXEC \| F_SEAL_SHRINK \| F_SEAL_GROW \| \ + F_SEAL_WRITE \| F_SEAL_FUTURE_WRITE) + #define TEST_SESSION_NAME "test-session" #define TEST_MEMFD_TOKEN 0x1A +#define TEST_EXEC_MEMFD_TOKEN 0x1B +#define TEST_NX_MEMFD_TOKEN 0x1C #define TEST_MEMFD_DATA "hello kexec world" / Constants for the state-tracking mechanism, specific to this test file. / #define STATE_SESSION_NAME "kexec_simple_state" #define STATE_MEMFD_TOKEN 999 +static void create_and_preserve_exec_memfd(int session_fd) +{ + struct liveupdate_session_preserve_fd arg = { + .size = sizeof(arg), + .token = TEST_EXEC_MEMFD_TOKEN, + }; + int mfd, seals; + + mfd = memfd_create("exec-mode-test", MFD_ALLOW_SEALING \| MFD_EXEC); + if (mfd < 0) { + / vm.memfd_noexec=2 refuses the MFD_EXEC opt-out. / + if (errno == EACCES) + ksft_exit_skip("vm.memfd_noexec forbids MFD_EXEC\n"); + fail_exit("memfd_create for execute-mode test"); + } + + if (fchmod(mfd, 0700) < 0) + fail_exit("fchmod for execute-mode test"); + if (fcntl(mfd, F_ADD_SEALS, F_SEAL_EXEC) < 0) + fail_exit("F_ADD_SEALS for execute-mode test"); + + / The execute bits pull in the write seals: record the whole set. / + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for execute-mode test"); + if (seals != F_WX_SEALS) + ksft_exit_fail_msg("execute-mode seals 0x%x != 0x%x\n", seals, + F_WX_SEALS); + ksft_print_msg("[STAGE 1] exec-mode memfd: execute mask 0100, seals 0x%x\n", + seals); + + arg.fd = mfd; + if (ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, &arg) < 0) + fail_exit("preserve execute-mode memfd"); + + close(mfd); +} + +static void restore_and_verify_exec_memfd(int session_fd) +{ + struct liveupdate_session_retrieve_fd arg = { + .size = sizeof(arg), + .token = TEST_EXEC_MEMFD_TOKEN, + }; + struct stat st; + int mfd, seals; + + if (ioctl(session_fd, LIVEUPDATE_SESSION_RETRIEVE_FD, &arg) < 0) + fail_exit("retrieve execute-mode memfd"); + mfd = arg.fd; + + if (fstat(mfd, &st) < 0) + fail_exit("fstat execute-mode memfd"); + if ((st.st_mode & 0111) != 0100) + ksft_exit_fail_msg("execute mask changed across kexec: 0%o != 0100\n", + st.st_mode & 0111); + + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for execute-mode test"); + if (seals != F_WX_SEALS) + ksft_exit_fail_msg("seals changed across kexec: 0x%x != 0x%x\n", + seals, F_WX_SEALS); + + ksft_print_msg("[STAGE 2] exec-mode memfd: execute mask 0%o, seals 0x%x\n", + st.st_mode & 0111, seals); + + close(mfd); +} + +/ + * The originally reported case: a memfd without execute bits and with + * F_SEAL_EXEC (what memfd_create(MFD_NOEXEC_SEAL) and vm.memfd_noexec=2 + * produce) has to come back without execute bits, with the same seal set, and + * still writable by its owner -- F_SEAL_EXEC must not drag in the write seals + * for a memfd that has no execute bits. + / +static void create_and_preserve_nx_memfd(int session_fd) +{ + struct liveupdate_session_preserve_fd arg = { + .size = sizeof(arg), + .token = TEST_NX_MEMFD_TOKEN, + }; + struct stat st; + int mfd, seals; + + mfd = memfd_create("nx-mode-test", MFD_ALLOW_SEALING \| MFD_NOEXEC_SEAL); + if (mfd < 0) + fail_exit("memfd_create for NX-mode test"); + + if (fstat(mfd, &st) < 0) + fail_exit("fstat for NX-mode test"); + if (st.st_mode & 0111) + ksft_exit_fail_msg("NX-mode memfd has execute bits (0%o)\n", + st.st_mode); + + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for NX-mode test"); + if (seals != F_SEAL_EXEC) + ksft_exit_fail_msg("NX-mode seals 0x%x != 0x%x\n", seals, + F_SEAL_EXEC); + + if (pwrite(mfd, TEST_MEMFD_DATA, sizeof(TEST_MEMFD_DATA) - 1, 0) != + sizeof(TEST_MEMFD_DATA) - 1) + fail_exit("NX-mode memfd is not writable"); + + ksft_print_msg("[STAGE 1] NX-mode memfd: execute mask 0000, seals 0x%x\n", + seals); + + arg.fd = mfd; + if (ioctl(session_fd, LIVEUPDATE_SESSION_PRESERVE_FD, &arg) < 0) + fail_exit("preserve NX-mode memfd"); + + close(mfd); +} + +static void restore_and_verify_nx_memfd(int session_fd) +{ + struct liveupdate_session_retrieve_fd arg = { + .size = sizeof(arg), + .token = TEST_NX_MEMFD_TOKEN, + }; + char buf[sizeof(TEST_MEMFD_DATA)] = {0}; + struct stat st; + int mfd, seals; + + if (ioctl(session_fd, LIVEUPDATE_SESSION_RETRIEVE_FD, &arg) < 0) + fail_exit("retrieve NX-mode memfd"); + mfd = arg.fd; + + if (fstat(mfd, &st) < 0) + fail_exit("fstat NX-mode memfd"); + if (st.st_mode & 0111) + ksft_exit_fail_msg("NX memfd came back executable: execute mask 0%o\n", + st.st_mode & 0111); + + seals = fcntl(mfd, F_GET_SEALS); + if (seals < 0) + fail_exit("F_GET_SEALS for NX-mode test"); + if (seals != F_SEAL_EXEC) + ksft_exit_fail_msg("NX memfd seals 0x%x != 0x%x\n", seals, + F_SEAL_EXEC); + + if (pread(mfd, buf, sizeof(buf) - 1, 0) != sizeof(buf) - 1) + fail_exit("pread NX-mode memfd"); + if (strcmp(buf, TEST_MEMFD_DATA)) + ksft_exit_fail_msg("NX memfd data changed: %s\n", buf); + + if (pwrite(mfd, "x", 1, 0) != 1) + ksft_exit_fail_msg("NX memfd is not writable by its owner\n"); + + ksft_print_msg("[STAGE 2] NX-mode memfd: execute mask 0000, seals 0x%x, writable\n", + seals); + + close(mfd); +} + / Stage 1: Executed before the kexec reboot. */ static void run_stage_1(int luo_fd) { @@ -40,6 +236,12 @@ static void run_stage_1(int luo_fd) TEST_MEMFD_TOKEN); } + ksft_print_msg("[STAGE 1] Preserving mode 0700 + F_SEAL_EXEC memfd...\n"); + create_and_preserve_exec_memfd(session_fd); + + ksft_print_msg("[STAGE 1] Preserving NX (no execute bits) + F_SEAL_EXEC memfd...\n"); + create_and_preserve_nx_memfd(session_fd); + close(luo_fd); daemonize_and_wait(); } @@ -68,6 +270,12 @@ static void run_stage_2(int luo_fd, int state_session_fd) fail_exit("restore_and_verify_memfd for token %#x", TEST_MEMFD_TOKEN); close(mfd); + ksft_print_msg("[STAGE 2] Verifying exact execute-mode round trip...\n"); + restore_and_verify_exec_memfd(session_fd); + + ksft_print_msg("[STAGE 2] Verifying NX round trip...\n"); + restore_and_verify_nx_memfd(session_fd); + ksft_print_msg("[STAGE 2] Test data verified successfully.\n"); ksft_print_msg("[STAGE 2] Finalizing test session...\n"); if (luo_session_finish(session_fd) < 0)
63/3	2026/10/14 08:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12113 output: 41 thoughts: 415 Thoughts: KMSAN Fuzzing Evaluation Alright, let's get down to brass tacks. I need to figure out if this patch series warrants a dedicated KMSAN fuzzing session. The instructions are clear: NeedsKMSAN only if the code introduces or exposes uninitialized memory risks that are specifically detected by KMSAN. Anything that KASAN or LOCKDEP already catches – out-of-bounds, overflows, null pointer derefs, deadlocks, use-after-frees – is a no-go for NeedsKMSAN. If the stack/heap structures are fully initialized, or there's no risk of uninitialized memory usage or info-leaks, then it's `NeedsKMSAN=false`. So, let's dive into this patch. First up is `include/linux/kho/abi/memfd.h`. We've got new macros: `MEMFD_LUO_FL_EXEC_USR`, `MEMFD_LUO_FL_EXEC_GRP`, `MEMFD_LUO_FL_EXEC_OTH`, and so on. They look like they're related to execution permissions in the memfd context. Now, I need to see what's going on with `struct memfd_luo_ser` in that header. I'll need to use either `read-file` or `grepper` to get a handle on the data structure and see if there's any hint of uninitialized memory. That's the key: does this introduce a new KMSAN-specific vulnerability? I'll need to scrutinize the `struct memfd_luo_ser` and how it is used.
64/3	2026/10/14 08:48	tool	grepper	0m Args: { "Expression": "struct memfd_luo_ser", "PathPrefixes": [ "include/linux/kho/abi/memfd.h" ] } 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=53=struct memfd_luo_folio_ser {\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-80- */\ninclude/linux/kho/abi/memfd.h:81:struct memfd_luo_ser {\ninclude/linux/kho/abi/memfd.h-82-\tu64 pos;\n" }
65/3	2026/10/14 08:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13208 output: 39 thoughts: 33 Thoughts: Here's a summary of my thought process, as requested: Diving into `memfd.h` for ABI Details Okay, time to get specific. I need to understand the memory file descriptor (memfd) ABI, particularly the definitions around lines 70 to 100 within `include/linux/kho/abi/memfd.h`. I'm going to start by reading those lines directly with `read-file`. This should give me the core definitions of structures, enums, or macros related to how memfds are intended to be used and interacted with at the system call level. This is the starting point to understand the specifics. I'm hoping to quickly identify any key data structures or flags exposed through the ABI in this section.
66/3	2026/10/14 08:48	tool	read-file	0m Args: { "File": "include/linux/kho/abi/memfd.h", "FirstLine": 70, "LineCount": 40 } Results: { "Contents": " 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 85:\t\tu32 flags;\n 86:\t\tu64 nr_folios;\n 87:\t\tstruct kho_vmalloc folios;\n 88:\t} __packed;\n 89:\t\n 90:\t/\n 91:\t * The execute permission bits are packed in user/group/other order. A record\n 92:\t * with none of these flags set is restored without execute permissions, which\n 93:\t * is also the safe interpretation for records written before these flags\n 94:\t * existed.\n 95:\t /\n 96:\t#define MEMFD_LUO_FL_EXEC_USR\t\tBIT(0)\n 97:\t#define MEMFD_LUO_FL_EXEC_GRP\t\tBIT(1)\n 98:\t#define MEMFD_LUO_FL_EXEC_OTH\t\tBIT(2)\n 99:\t#define MEMFD_LUO_FL_EXEC_MASK\t\t(MEMFD_LUO_FL_EXEC_USR \| \\\n 100:\t\t\t\t\t\t MEMFD_LUO_FL_EXEC_GRP \| \\\n 101:\t\t\t\t\t\t MEMFD_LUO_FL_EXEC_OTH)\n 102:\t#define MEMFD_LUO_ALL_FLAGS\t\tMEMFD_LUO_FL_EXEC_MASK\n 103:\t\n 104:\t/ The compatibility string for memfd file handler /\n 105:\t#define MEMFD_LUO_FH_COMPATIBLE\t\t\"memfd-v3\"\n 106:\t/\n 107:\t * Records written before the execute-bit flags existed. They carry no flag\n 108:\t * bits and are restored without execute permissions: the flags cannot tell\n 109:\t * \"the execute bits were clear\" and \"the writer did not know about the flags\"\n" }
67/3	2026/10/14 08:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14164 output: 37 thoughts: 46 Thoughts: Here's my analysis of the provided text, rendered in the first person, assuming an expert user: Diving into the `memfd_luo_ser` Structure Okay, so I need to understand how the `struct memfd_luo_ser` is allocated and then utilized within the `mm/memfd_luo.c` file. This is crucial for understanding the memory management implications and the overall operation of memfd_luo. I'll open up `mm/memfd_luo.c` and start digging in to see how this all comes together. Time to get my hands dirty and examine the actual code. Let's see what interesting techniques they've employed here.
68/3	2026/10/14 08:48	tool	grepper	0m Args: { "Expression": "memfd_luo_preserve", "PathPrefixes": [ "mm/memfd_luo.c" ] } Results: { "Output": "mm/memfd_luo.c=112=static umode_t memfd_luo_restore_exec_mode(u32 flags)\n--\nmm/memfd_luo.c-125-\nmm/memfd_luo.c:126:static int memfd_luo_preserve_folios(struct file file,\nmm/memfd_luo.c-127-\t\t\t\t struct kho_vmalloc kho_vmalloc,\n--\nmm/memfd_luo.c=270=static void memfd_luo_unpreserve_folios(struct kho_vmalloc kho_vmalloc,\n--\nmm/memfd_luo.c-296-\nmm/memfd_luo.c:297:static int memfd_luo_preserve(struct liveupdate_file_op_args args)\nmm/memfd_luo.c-298-{\n--\nmm/memfd_luo.c-349-\nmm/memfd_luo.c:350:\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\nmm/memfd_luo.c-351-\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n--\nmm/memfd_luo.c=722=static const struct liveupdate_file_ops memfd_luo_file_ops = {\n--\nmm/memfd_luo.c-726-\t.retrieve = memfd_luo_retrieve,\nmm/memfd_luo.c:727:\t.preserve = memfd_luo_preserve,\nmm/memfd_luo.c-728-\t.unpreserve = memfd_luo_unpreserve,\n--\nmm/memfd_luo.c=752=static const struct liveupdate_file_ops memfd_luo_file_ops_v2 = {\n--\nmm/memfd_luo.c-756-\t.retrieve = memfd_luo_retrieve,\nmm/memfd_luo.c:757:\t.preserve = memfd_luo_preserve,\nmm/memfd_luo.c-758-\t.unpreserve = memfd_luo_unpreserve,\n" }
69/3	2026/10/14 08:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14962 output: 37 thoughts: 37 Thoughts: Okay, let's dive into this. Here's my take on those lines of code: Analyzing `memfd_luo_preserve` in `mm/memfd_luo.c` Alright, I'm heading into `mm/memfd_luo.c`, specifically focusing on the `memfd_luo_preserve` function, roughly from lines 295 to 365. This is where the core logic for preserving memory backing the memfd file descriptor resides, and I need to understand it at a granular level. I anticipate it deals with the more intricate details of ensuring the memory doesn't get swapped out or reclaimed when a process wants to keep it around. I want to see how it interacts with the underlying page tables, especially in the context of file-backed memory and the implications on swap behavior. I'm keen to see if they're using specific flags or operations on the pages to mark them as 'locked' or 'pinned'. I also need to understand any subtle interactions with the VM subsystem, such as how it coordinates with memory reclaim and migration. Finally, I'll be looking for any potential race conditions or synchronization issues in that code, as that area is very sensitive to such issues.
70/3	2026/10/14 08:48	tool	read-file	0m Args: { "File": "mm/memfd_luo.c", "FirstLine": 295, "LineCount": 65 } Results: { "Contents": " 295:\t}\n 296:\t\n 297:\tstatic int memfd_luo_preserve(struct liveupdate_file_op_args args)\n 298:\t{\n 299:\t\tstruct inode inode = file_inode(args-\u003efile);\n 300:\t\tstruct memfd_luo_folio_ser folios_ser;\n 301:\t\tstruct memfd_luo_ser ser;\n 302:\t\tu64 nr_folios, inode_size;\n 303:\t\tint err = 0, seals;\n 304:\t\n 305:\t\tinode_lock(inode);\n 306:\t\tshmem_freeze(inode, true);\n 307:\t\n 308:\t\t/* Allocate the main serialization structure in preserved memory /\n 309:\t\tser = kho_alloc_preserve(sizeof(ser));\n 310:\t\tif (IS_ERR(ser)) {\n 311:\t\t\terr = PTR_ERR(ser);\n 312:\t\t\tgoto err_unlock;\n 313:\t\t}\n 314:\t\n 315:\t\tseals = memfd_get_seals(args-\u003efile);\n 316:\t\tif (seals \u003c 0) {\n 317:\t\t\terr = seals;\n 318:\t\t\tgoto err_free_ser;\n 319:\t\t}\n 320:\t\n 321:\t\t/* Make sure the file only has the seals supported by this version. /\n 322:\t\tif (seals \u0026 ~MEMFD_LUO_ALL_SEALS) {\n 323:\t\t\terr = -EOPNOTSUPP;\n 324:\t\t\tgoto err_free_ser;\n 325:\t\t}\n 326:\t\n 327:\t\tser-\u003epos = args-\u003efile-\u003ef_pos;\n 328:\t\tinode_size = i_size_read(inode);\n 329:\t\n 330:\t\t/\n 331:\t\t * memfd_pin_folios() caps at UINT_MAX folios; refuse larger\n 332:\t\t * files to avoid silently preserving only a prefix.\n 333:\t\t /\n 334:\t\tif (DIV_ROUND_UP_ULL(inode_size, PAGE_SIZE) \u003e UINT_MAX) {\n 335:\t\t\terr = -EFBIG;\n 336:\t\t\tgoto err_free_ser;\n 337:\t\t}\n 338:\t\n 339:\t\tser-\u003esize = inode_size;\n 340:\t\tser-\u003eseals = seals;\n 341:\t\n 342:\t\t/\n 343:\t\t * F_SEAL_EXEC freezes each execute permission bit independently, so\n 344:\t\t * preserve the complete user/group/other execute mask. A record with no\n 345:\t\t * execute flags is restored without execute permissions, which is also\n 346:\t\t * the safe interpretation for records written before these flags existed.\n 347:\t\t */\n 348:\t\tmemfd_luo_record_exec_mode(ser, inode-\u003ei_mode);\n 349:\t\n 350:\t\terr = memfd_luo_preserve_folios(args-\u003efile, \u0026ser-\u003efolios,\n 351:\t\t\t\t\t\t\u0026folios_ser, \u0026nr_folios);\n 352:\t\tif (err)\n 353:\t\t\tgoto err_free_ser;\n 354:\t\n 355:\t\tser-\u003enr_folios = nr_folios;\n 356:\t\tinode_unlock(inode);\n 357:\t\n 358:\t\targs-\u003eprivate_data = folios_ser;\n 359:\t\targs-\u003eserialized_data = virt_to_phys(ser);\n" }
71/3	2026/10/14 08:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16262 output: 19 thoughts: 29 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into `kho_alloc_preserve` Alright, let's dissect this line: `kho_alloc_preserve(sizeof(ser))`. The first thing I see is `kho_alloc_preserve`. Clearly, I need to understand this function. It's obviously designed to allocate memory, but the "preserve" part suggests it might be doing something specific with the allocation, perhaps maintaining some state or preventing unwanted deallocation. I need to trace this back. Then, there's `sizeof(ser)`. That's straightforward: it's calculating the size, in bytes, of whatever `ser` points to. Makes perfect sense. The function will allocate enough memory to hold an instance of whatever type `ser` is a pointer to. Alright, let's see what `kho_alloc_preserve` is all about. Time to consult the documentation or source code!
72/3	2026/10/14 08:49	tool	grepper	0m Args: { "Expression": "kho_alloc_preserve" } Results: { "Output": "include/linux/kexec_handover.h=28=void kho_unpreserve_vmalloc(struct kho_vmalloc preservation);\ninclude/linux/kexec_handover.h:29:void kho_alloc_preserve(size_t size);\ninclude/linux/kexec_handover.h-30-void kho_unpreserve_free(void mem);\n--\ninclude/linux/kexec_handover.h=74=static inline void kho_unpreserve_vmalloc(struct kho_vmalloc preservation) { }\ninclude/linux/kexec_handover.h-75-\ninclude/linux/kexec_handover.h:76:static inline void kho_alloc_preserve(size_t size)\ninclude/linux/kexec_handover.h-77-{\n--\nkernel/liveupdate/kexec_handover.c=1230=EXPORT_SYMBOL_GPL(kho_restore_vmalloc);\n--\nkernel/liveupdate/kexec_handover.c-1232-/\nkernel/liveupdate/kexec_handover.c:1233: kho_alloc_preserve - Allocate, zero, and preserve memory.\nkernel/liveupdate/kexec_handover.c-1234- * @size: The number of bytes to allocate.\n--\nkernel/liveupdate/kexec_handover.c-1245- /\nkernel/liveupdate/kexec_handover.c:1246:void kho_alloc_preserve(size_t size)\nkernel/liveupdate/kexec_handover.c-1247-{\n--\nkernel/liveupdate/kexec_handover.c-1269-}\nkernel/liveupdate/kexec_handover.c:1270:EXPORT_SYMBOL_GPL(kho_alloc_preserve);\nkernel/liveupdate/kexec_handover.c-1271-\n--\nkernel/liveupdate/kexec_handover.c-1273- * kho_unpreserve_free - Unpreserve and free memory.\nkernel/liveupdate/kexec_handover.c:1274: * @mem: Pointer to the memory allocated by kho_alloc_preserve().\nkernel/liveupdate/kexec_handover.c-1275- \n--\nkernel/liveupdate/kexec_handover.c-1277- pages back to the system. This function should be called to clean up\nkernel/liveupdate/kexec_handover.c:1278: * memory allocated with kho_alloc_preserve().\nkernel/liveupdate/kexec_handover.c-1279- /\n--\nkernel/liveupdate/kexec_handover.c=1291=EXPORT_SYMBOL_GPL(kho_unpreserve_free);\n--\nkernel/liveupdate/kexec_handover.c-1299- to take ownership of and free a memory region that was preserved by the\nkernel/liveupdate/kexec_handover.c:1300: * old kernel using kho_alloc_preserve().\nkernel/liveupdate/kexec_handover.c-1301- \n--\nkernel/liveupdate/kexec_handover.c=1498=static __init int kho_out_kexec_metadata(void)\n--\nkernel/liveupdate/kexec_handover.c-1502-\nkernel/liveupdate/kexec_handover.c:1503:\tmetadata = kho_alloc_preserve(sizeof(metadata));\nkernel/liveupdate/kexec_handover.c-1504-\tif (IS_ERR(metadata))\n--\nkernel/liveupdate/kexec_handover.c=1537=static __init int kho_init(void)\n--\nkernel/liveupdate/kexec_handover.c-1551-\nkernel/liveupdate/kexec_handover.c:1552:\tkho_out.fdt = kho_alloc_preserve(PAGE_SIZE);\nkernel/liveupdate/kexec_handover.c-1553-\tif (IS_ERR(kho_out.fdt)) {\n--\nkernel/liveupdate/kho_block.c=73=static struct kho_block_header_ser kho_block_alloc_ser(struct kho_block_set bs)\n--\nkernel/liveupdate/kho_block.c-75-\tWARN_ON_ONCE(bs-\u003eincoming);\nkernel/liveupdate/kho_block.c:76:\treturn kho_alloc_preserve(KHO_BLOCK_SIZE);\nkernel/liveupdate/kho_block.c-77-}\n--\nkernel/liveupdate/luo_core.c=154=static int __init luo_state_setup(void)\n--\nkernel/liveupdate/luo_core.c-158-\nkernel/liveupdate/luo_core.c:159:\tluo_ser = kho_alloc_preserve(sizeof(luo_ser));\nkernel/liveupdate/luo_core.c-160-\tif (IS_ERR(luo_ser)) {\n--\nkernel/liveupdate/luo_flb.c=552=int __init luo_flb_setup_outgoing(u64 flbs_pa)\n--\nkernel/liveupdate/luo_flb.c-555-\nkernel/liveupdate/luo_flb.c:556:\theader_ser = kho_alloc_preserve(LUO_FLB_PGCNT \u003c\u003c PAGE_SHIFT);\nkernel/liveupdate/luo_flb.c-557-\tif (IS_ERR(header_ser))\n--\nmm/memfd_luo.c=297=static int memfd_luo_preserve(struct liveupdate_file_op_args args)\n--\nmm/memfd_luo.c-308-\t/ Allocate the main serialization structure in preserved memory /\nmm/memfd_luo.c:309:\tser = kho_alloc_preserve(sizeof(ser));\nmm/memfd_luo.c-310-\tif (IS_ERR(ser)) {\n" }
73/3	2026/10/14 08:49	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18010 output: 41 thoughts: 62 Thoughts: Here's my summary, as I see it: Verifying `kho_alloc_preserve`'s Behavior in Liveupdate Okay, so the documentation for `kho_alloc_preserve` claims it allocates, zeros, and preserves memory. That's the stated intent, but we know documentation can sometimes be aspirational rather than reflective of reality, or even misleading. I'm going to quickly cross-reference that claim with a real-world use case to confirm the behavior matches the documentation. Specifically, I'll drill into `kernel/liveupdate/kexec_handover.c` and take a look at lines 1240-1270. This should give me a solid data point on how this function is actually being used, and if its behavior aligns with the "allocate, zero, and preserve" description in a critical area. It’s always good practice to verify assumptions, especially when dealing with memory allocation in a liveupdate context where correctness is paramount.
74/3	2026/10/14 08:49	tool	read-file	0m Args: { "File": "kernel/liveupdate/kexec_handover.c", "FirstLine": 1240, "LineCount": 30 } Results: { "Contents": "1240:\t * Note: The actual allocated size will be rounded up to the nearest\n1241:\t * power-of-two page boundary.\n1242:\t \n1243:\t @return A virtual pointer to the allocated and preserved memory on success,\n1244:\t * or an ERR_PTR() encoded error on failure.\n1245:\t /\n1246:\tvoid kho_alloc_preserve(size_t size)\n1247:\t{\n1248:\t\tstruct folio *folio;\n1249:\t\tint order, ret;\n1250:\t\n1251:\t\tif (!size)\n1252:\t\t\treturn ERR_PTR(-EINVAL);\n1253:\t\n1254:\t\torder = get_order(size);\n1255:\t\tif (order \u003e MAX_PAGE_ORDER)\n1256:\t\t\treturn ERR_PTR(-E2BIG);\n1257:\t\n1258:\t\tfolio = folio_alloc(GFP_KERNEL \| __GFP_ZERO, order);\n1259:\t\tif (!folio)\n1260:\t\t\treturn ERR_PTR(-ENOMEM);\n1261:\t\n1262:\t\tret = kho_preserve_folio(folio);\n1263:\t\tif (ret) {\n1264:\t\t\tfolio_put(folio);\n1265:\t\t\treturn ERR_PTR(ret);\n1266:\t\t}\n1267:\t\n1268:\t\treturn folio_address(folio);\n1269:\t}\n" }
75/3	2026/10/14 08:49	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18728 output: 36 thoughts: 2379 Thoughts: Analyzing the LUO Kexec Handover Code for KMSAN Implications Alright, let's break this down. First, `kho_alloc_preserve` uses `__GFP_ZERO`. This means the `memfd_luo_ser` struct (`ser` in the code) is guaranteed to be zero-initialized when allocated. That's good from a KMSAN perspective. No worries there. The code modifies the `ser` struct based on file mode (executable bits) via `memfd_luo_record_exec_mode` and restores the executable mode from `ser` on retrieval with `memfd_luo_restore_exec_mode`. The restoration happens in `memfd_luo_retrieve`, where `exec_mode` is restored to `file->f_inode->i_mode`. The important thing here is that the executable bits are derived from the existing inode, modified, stored in the `ser` and restored. The presence of `SHMEM_F_SEAL_STATE_FROZEN` is interesting. The code uses this flag to prevent modifications to the file's seals and mode after the "LUO final snapshot". This is enforced in various places, like `memfd_add_seals` and `shmem_set_acl`, and inside `shmem_setattr`. Now, digging deeper. `memfd_luo_can_preserve` checks `!IS_PRIVATE(inode)` which indicates that SysV SHM is excluded. The important part is that the code freezes and unfreezes the seal state via `shmem_freeze_seal_state` calls. The core logic within the series happens in `memfd_luo_freeze`, `memfd_luo_unfreeze`, and `memfd_luo_unpreserve`. `memfd_luo_freeze` records the executable mode from the inode, the seals and the file's position to `ser`. `memfd_luo_unfreeze` and `memfd_luo_unpreserve` simply unfreeze the seal state. `memfd_luo_retrieve` restores the `exec_mode` from `ser` to the inode. We have a backwards-compatible `memfd_luo_handler_v2` and selftests, this is for code that will persist into later versions. Now, the critical question: are any kernel structures sent to userspace? Specifically, is the `memfd_luo_ser` structure or data derived from it passed to userspace via any of the listed methods in the instructions? NO, `memfd_luo_ser` is not directly exposed to userspace via copy_to_user, put_user, netlink, ioctl, socket, or BPF. It is used internally for the kexec handover. It only lives within the kernel address space. The `LIVEUPDATE_SESSION_PRESERVE_FD` and `LIVEUPDATE_SESSION_RETRIEVE_FD` ioctls need more examination, but they don't appear to transfer this structure directly. The executable mode bits ARE set from the internal structure, and they can be observed by an unprivileged user from the permissions on a file. Based on this analysis, the code primarily involves internal kernel data structures and modifications to file metadata within the kernel's context. Since no kernel structures are being passed to userspace and the `memfd_luo_ser` struct is zero-initialized, I don't see any immediate risk of uninitialized memory usage or info-leaks directly introduced by this code. The code is primarily concerned with preserving the executable mode during a kexec handover.
76/3	2026/10/14 08:49	tool	grepper	0m Args: { "Expression": "LIVEUPDATE_SESSION_", "PathPrefixes": [ "kernel/liveupdate/", "include/" ] } Results: { "Output": "include/linux/kho/abi/luo.h=131=struct luo_session_ser {\ninclude/linux/kho/abi/luo.h:132:\tchar name[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/linux/kho/abi/luo.h-133-\tstruct luo_file_set_ser file_set_ser;\n--\ninclude/uapi/linux/liveupdate.h-46-/* The maximum length of session name including null termination /\ninclude/uapi/linux/liveupdate.h:47:#define LIVEUPDATE_SESSION_NAME_LENGTH 64\ninclude/uapi/linux/liveupdate.h-48-\n--\ninclude/uapi/linux/liveupdate.h=57=enum {\n--\ninclude/uapi/linux/liveupdate.h-69- @name:\tInput; A null-terminated string for the session name, max\ninclude/uapi/linux/liveupdate.h:70: \t\tlength %LIVEUPDATE_SESSION_NAME_LENGTH including termination\ninclude/uapi/linux/liveupdate.h-71- \t\tcharacter.\n--\ninclude/uapi/linux/liveupdate.h=78=struct liveupdate_ioctl_create_session {\n--\ninclude/uapi/linux/liveupdate.h-80-\t__s32\t\tfd;\ninclude/uapi/linux/liveupdate.h:81:\t__u8\t\tname[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/uapi/linux/liveupdate.h-82-};\n--\ninclude/uapi/linux/liveupdate.h-103- * operations, such as restoring individual file descriptors with\ninclude/uapi/linux/liveupdate.h:104: * LIVEUPDATE_SESSION_RETRIEVE_FD.\ninclude/uapi/linux/liveupdate.h-105- \n--\ninclude/uapi/linux/liveupdate.h=113=struct liveupdate_ioctl_retrieve_session {\n--\ninclude/uapi/linux/liveupdate.h-115-\t__s32\t\tfd;\ninclude/uapi/linux/liveupdate.h:116:\t__u8\t\tname[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/uapi/linux/liveupdate.h-117-};\n--\ninclude/uapi/linux/liveupdate.h-124-/\ninclude/uapi/linux/liveupdate.h:125: struct liveupdate_session_preserve_fd - ioctl(LIVEUPDATE_SESSION_PRESERVE_FD)\ninclude/uapi/linux/liveupdate.h-126- * @size: Input; sizeof(struct liveupdate_session_preserve_fd)\n--\ninclude/uapi/linux/liveupdate.h-141- * This token confirms the FD is targeted for preservation and is required for\ninclude/uapi/linux/liveupdate.h:142: * the subsequent %LIVEUPDATE_SESSION_RETRIEVE_FD call after the live update.\ninclude/uapi/linux/liveupdate.h-143- \n--\ninclude/uapi/linux/liveupdate.h=148=struct liveupdate_session_preserve_fd {\n--\ninclude/uapi/linux/liveupdate.h-153-\ninclude/uapi/linux/liveupdate.h:154:#define LIVEUPDATE_SESSION_PRESERVE_FD\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-155-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_PRESERVE_FD)\n--\ninclude/uapi/linux/liveupdate.h-157-/\ninclude/uapi/linux/liveupdate.h:158: struct liveupdate_session_retrieve_fd - ioctl(LIVEUPDATE_SESSION_RETRIEVE_FD)\ninclude/uapi/linux/liveupdate.h-159- * @size: Input; sizeof(struct liveupdate_session_retrieve_fd)\n--\ninclude/uapi/linux/liveupdate.h=178=struct liveupdate_session_retrieve_fd {\n--\ninclude/uapi/linux/liveupdate.h-183-\ninclude/uapi/linux/liveupdate.h:184:#define LIVEUPDATE_SESSION_RETRIEVE_FD\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-185-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_RETRIEVE_FD)\n--\ninclude/uapi/linux/liveupdate.h-187-/*\ninclude/uapi/linux/liveupdate.h:188: struct liveupdate_session_finish - ioctl(LIVEUPDATE_SESSION_FINISH)\ninclude/uapi/linux/liveupdate.h-189- * @size: Input; sizeof(struct liveupdate_session_finish)\n--\ninclude/uapi/linux/liveupdate.h-196- * This ioctl must be called once all required file descriptors for the session\ninclude/uapi/linux/liveupdate.h:197: * have been successfully retrieved (using %LIVEUPDATE_SESSION_RETRIEVE_FD) and\ninclude/uapi/linux/liveupdate.h-198- * are fully restored from the userspace and kernel perspective.\n--\ninclude/uapi/linux/liveupdate.h=211=struct liveupdate_session_finish {\n--\ninclude/uapi/linux/liveupdate.h-215-\ninclude/uapi/linux/liveupdate.h:216:#define LIVEUPDATE_SESSION_FINISH\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-217-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FINISH)\n--\ninclude/uapi/linux/liveupdate.h-219-/*\ninclude/uapi/linux/liveupdate.h:220: struct liveupdate_session_get_name - ioctl(LIVEUPDATE_SESSION_GET_NAME)\ninclude/uapi/linux/liveupdate.h-221- * @size: Input; sizeof(struct liveupdate_session_get_name)\n--\ninclude/uapi/linux/liveupdate.h=230=struct liveupdate_session_get_name {\n--\ninclude/uapi/linux/liveupdate.h-232-\t__u32\t\treserved;\ninclude/uapi/linux/liveupdate.h:233:\t__u8\t\tname[LIVEUPDATE_SESSION_NAME_LENGTH];\ninclude/uapi/linux/liveupdate.h-234-};\ninclude/uapi/linux/liveupdate.h-235-\ninclude/uapi/linux/liveupdate.h:236:#define LIVEUPDATE_SESSION_GET_NAME\t\t\t\t\t\\\ninclude/uapi/linux/liveupdate.h-237-\t_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME)\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_session.c=373=static const struct luo_ioctl_op luo_session_ioctl_ops[] = {\nkernel/liveupdate/luo_session.c:374:\tIOCTL_OP(LIVEUPDATE_SESSION_FINISH, luo_session_finish,\nkernel/liveupdate/luo_session.c-375-\t\t struct liveupdate_session_finish, reserved, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:376:\tIOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,\nkernel/liveupdate/luo_session.c-377-\t\t struct liveupdate_session_preserve_fd, token, LUO_IOCTL_OUTGOING),\nkernel/liveupdate/luo_session.c:378:\tIOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,\nkernel/liveupdate/luo_session.c-379-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),\nkernel/liveupdate/luo_session.c:380:\tIOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,\nkernel/liveupdate/luo_session.c-381-\t\t struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_ALL),\n--\nkernel/liveupdate/luo_session.c=463=int luo_session_create(const char name, struct file filep)\nkernel/liveupdate/luo_session.c-464-{\nkernel/liveupdate/luo_session.c:465:\tsize_t len = strnlen(name, LIVEUPDATE_SESSION_NAME_LENGTH);\nkernel/liveupdate/luo_session.c-466-\tstruct luo_session session;\n--\nkernel/liveupdate/luo_session.c-468-\nkernel/liveupdate/luo_session.c:469:\tif (len == 0 \|\| len \u003e LIVEUPDATE_SESSION_NAME_LENGTH - 1)\nkernel/liveupdate/luo_session.c-470-\t\treturn -EINVAL;\n" }
77/3	2026/10/14 08:49	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24251 output: 354 thoughts: 1996 Thoughts: KMSAN Assessment: Live Update Memfd Implementation Okay, let's break this down. The core function here, `LIVEUPDATE_SESSION_RETRIEVE_FD`, seems to be returning a file descriptor. The main concern, from a KMSAN perspective, is uninitialized memory. Let's trace it through: `luo_session_retrieve_fd` returns an `fd` without serializing anything to userspace directly. `memfd_luo_retrieve` is where things get interesting. We're receiving serialized data, allocating a shared memory file using `memfd_alloc_file`, and then setting the execution mode and seals. The important parts are the variables involved are all properly initialized. Specifically: * `memfd_luo_record_exec_mode` initializes `flags` to 0, and `ser` is allocated with `__GFP_ZERO`. `memfd_luo_restore_exec_mode` also initializes its `mode` to 0. * In `memfd_luo_retrieve`, `folios_ser` is initialized to NULL, `exec_mode` is assigned from a function that initializes its return, and all `err` return values are assigned before use. Error paths ensure allocated memory is freed or discarded. Now, looking at `memfd_luo_freeze` and `memfd_luo_unfreeze`, no uninitialized variables there either. `shmem_setattr`, `shmem_set_acl`, and `memfd_add_seals` seem to be making correct checks. No uninitialized memory is read. I've examined the code according to the four KMSAN criteria: 1. Kernel structures sent to userspace: Not present in this patch. 2. Conditional logic with uninitialized variables: Not present. All variables are initialized. 3. Complex data structures with uninitialized fields: Allocation with `__GFP_ZERO` handles initialization. 4. Bounds checks that could lead to uninitialized reads: Not present here. The patch modifies existing buffers, but it does not introduce new reads of uninitialized memory. The potential issues I see are around concurrency (locking), permission errors, and memory leaks. These are areas I'd watch for during review and testing, but KMSAN isn't the right tool for those issues. Therefore, running a dedicated KMSAN fuzzing session would not be justified. All the details and aspects seem to be checked and cleared. Time to make the call to `set-results`.
78/3	2026/10/14 08:49	tool	set-results	0m Args: { "KMSANReasoning": "The patch series updates memfd Live Update Orchestration (LUO) and shmem to preserve exact execute permission bits (user/group/other) across kexec reboots (supporting F_SEAL_EXEC), and freezes the seal/mode state during liveupdate to prevent divergence.\n\nAnalysis with respect to memory sanitizers:\n1. No uninitialized memory or info-leak risks:\n - The serialization record `struct memfd_luo_ser` is allocated via `kho_alloc_preserve()`, which internally uses `folio_alloc()` with `__GFP_ZERO`, ensuring all fields and padding are zero-initialized.\n - All newly added local variables (`flags`, `mode`, `folios_ser`) are explicitly initialized before use.\n - The serialized structure is exchanged internally between kernels during kexec handover (KHO) and is not copied to userspace. No data structures or padding are exposed to userspace via `copy_to_user`, ioctls, or netlink.\n2. KASAN/LOCKDEP applicability:\n - Any potential issues introduced by this patch revolve around concurrency/locking (`shmem_seal_state_frozen` lock discipline, inode lock serialization), file reference handling (`fput`), or folio lifetime management (`memfd_luo_discard_folios`), which are covered by standard KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nTherefore, this patch series does not introduce uninitialized memory read risks or kernel-to-user info-leaks, and a dedicated KMSAN session is not required.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch series updates memfd Live Update Orchestration (LUO) and shmem to preserve exact execute permission bits (user/group/other) across kexec reboots (supporting F_SEAL_EXEC), and freezes the seal/mode state during liveupdate to prevent divergence.\n\nAnalysis with respect to memory sanitizers:\n1. No uninitialized memory or info-leak risks:\n - The serialization record `struct memfd_luo_ser` is allocated via `kho_alloc_preserve()`, which internally uses `folio_alloc()` with `__GFP_ZERO`, ensuring all fields and padding are zero-initialized.\n - All newly added local variables (`flags`, `mode`, `folios_ser`) are explicitly initialized before use.\n - The serialized structure is exchanged internally between kernels during kexec handover (KHO) and is not copied to userspace. No data structures or padding are exposed to userspace via `copy_to_user`, ioctls, or netlink.\n2. KASAN/LOCKDEP applicability:\n - Any potential issues introduced by this patch revolve around concurrency/locking (`shmem_seal_state_frozen` lock discipline, inode lock serialization), file reference handling (`fput`), or folio lifetime management (`memfd_luo_discard_folios`), which are covered by standard KASAN, LOCKDEP, and standard kernel debugging facilities.\n\nTherefore, this patch series does not introduce uninitialized memory read risks or kernel-to-user info-leaks, and a dedicated KMSAN session is not required.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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