| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/10/09 09:33 | flow | patch-triage |
5mArgs:null Results: {
"EnableConfigs": null,
"FocusSymbols": [
"__vmap_pages_range_noflush",
"vmap_pages_range_noflush",
"vmap_page_range",
"kmsan_vmap_pages_range_noflush"
],
"KMSANReasoning": "The patch series improves error handling and unwinding during kernel virtual memory mapping (vmalloc/ioremap/percpu/kmsan shadow). Specifically, it ensures that partially installed page tables and KMSAN shadow/origin metadata mappings are cleanly unwound and unmapped upon failure within `vmap_pages_range_noflush()`, `__vmap_pages_range_noflush()`, `vmap_page_range()`, and `kmsan_vmap_pages_range_noflush()`, and removes redundant cleanup in callers.\n\nThese changes deal strictly with kernel page table management, TLB invalidation, and error unwinding. They do not introduce or modify any kernel structures exposed to user space, nor do they introduce any logic reading or branching on uninitialized stack or heap variables. Any potential bugs in this patch (such as incorrect address ranges, double unmaps, or page table corruption) fall under general memory management / page table errors, which are checked by standard kernel asserts and KASAN builds. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"NeedsKMSAN": false,
"Reasoning": "The patch alters core memory management code in mm/vmalloc.c, mm/percpu-vm.c, and mm/kmsan/shadow.c. It introduces new runtime assertions (WARN_ON_ONCE checks on address bounds and page shift) in __vmap_pages_range_noflush() and modifies error unwinding semantics so that partial page table mappings roll back automatically on failure across vmap_page_range(), __vmap_pages_range_noflush(), and kmsan_vmap_pages_range_noflush(). These code paths are reachable on amd64 in virtualized environments via standard vmalloc, vmap, and percpu allocations.",
"WorthFuzzing": true
} |
| 1/1 | 2026/10/09 09:33 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit 3eeb0ec9d1278ab64da2fcb0f06e870d40cc97bc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Fri Oct 9 09:33:29 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/arch/powerpc/kernel/isa-bridge.c b/arch/powerpc/kernel/isa-bridge.c\nindex 5c064485197a9..93029d85e6eaf 100644\n--- a/arch/powerpc/kernel/isa-bridge.c\n+++ b/arch/powerpc/kernel/isa-bridge.c\n@@ -46,9 +46,8 @@ static void remap_isa_base(phys_addr_t pa, unsigned long size)\n \tWARN_ON_ONCE(size \u0026 ~PAGE_MASK);\n \n \tif (slab_is_available()) {\n-\t\tif (vmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,\n-\t\t\t\t pgprot_noncached(PAGE_KERNEL)))\n-\t\t\tvunmap_range(ISA_IO_BASE, ISA_IO_BASE + size);\n+\t\tvmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,\n+\t\t\t\tpgprot_noncached(PAGE_KERNEL));\n \t} else {\n \t\tearly_ioremap_range(ISA_IO_BASE, pa, size,\n \t\t\t\tpgprot_noncached(PAGE_KERNEL));\ndiff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c\nindex e27342ef128b8..f74269636d5ec 100644\n--- a/arch/powerpc/kernel/pci_64.c\n+++ b/arch/powerpc/kernel/pci_64.c\n@@ -139,10 +139,8 @@ void __iomem *ioremap_phb(phys_addr_t paddr, unsigned long size)\n \n \taddr = (unsigned long)area-\u003eaddr;\n \tif (ioremap_page_range(addr, addr + size, paddr,\n-\t\t\tpgprot_noncached(PAGE_KERNEL))) {\n-\t\tvunmap_range(addr, addr + size);\n+\t\t\tpgprot_noncached(PAGE_KERNEL)))\n \t\treturn NULL;\n-\t}\n \n \treturn (void __iomem *)addr;\n }\ndiff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c\nindex 0c88d89bf0d68..2166086d3dc3b 100644\n--- a/mm/kmsan/shadow.c\n+++ b/mm/kmsan/shadow.c\n@@ -258,6 +258,10 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,\n \t\t\t\t\t o_pages, page_shift);\n \tkmsan_leave_runtime();\n \tif (mapped) {\n+\t\t/* Undo the shadow mapping set up above. */\n+\t\tkmsan_enter_runtime();\n+\t\t__vunmap_range_noflush(shadow_start, shadow_end);\n+\t\tkmsan_leave_runtime();\n \t\terr = mapped;\n \t\tgoto ret;\n \t}\ndiff --git a/mm/percpu-vm.c b/mm/percpu-vm.c\nindex 509d8901835cd..59d3a336a6bd1 100644\n--- a/mm/percpu-vm.c\n+++ b/mm/percpu-vm.c\n@@ -252,10 +252,11 @@ static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,\n \treturn 0;\n err:\n \tfor_each_possible_cpu(tcpu) {\n-\t\t__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),\n-\t\t\t\t page_end - page_start);\n+\t\t/* The failing CPU's partial mapping undoes itself */\n \t\tif (tcpu == cpu)\n \t\t\tbreak;\n+\t\t__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),\n+\t\t\t\t page_end - page_start);\n \t}\n \tpcpu_post_unmap_tlb_flush(chunk, page_start, page_end);\n \treturn err;\ndiff --git a/mm/vmalloc.c b/mm/vmalloc.c\nindex db669103dc666..e1b376f57dd25 100644\n--- a/mm/vmalloc.c\n+++ b/mm/vmalloc.c\n@@ -363,6 +363,9 @@ int vmap_page_range(unsigned long addr, unsigned long end,\n \tif (!err)\n \t\terr = kmsan_ioremap_page_range(addr, end, phys_addr, prot,\n \t\t\t\t\t ioremap_max_page_shift);\n+\tif (err)\n+\t\t__vunmap_range_noflush(addr, end);\n+\n \treturn err;\n }\n \n@@ -683,27 +686,35 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n \t\tpgprot_t prot, struct page **pages, unsigned int page_shift)\n {\n \tunsigned int i, nr = (end - addr) \u003e\u003e PAGE_SHIFT;\n+\tunsigned long start = addr;\n+\tint err = 0;\n+\n+\tif (WARN_ON_ONCE(addr \u003e= end))\n+\t\treturn -EINVAL;\n \n \tif (WARN_ON_ONCE(page_shift \u003c PAGE_SHIFT))\n \t\treturn -EINVAL;\n \n \tif (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||\n-\t\t\tpage_shift == PAGE_SHIFT)\n-\t\treturn vmap_small_pages_range_noflush(addr, end, prot, pages);\n-\n-\tfor (i = 0; i \u003c nr; i += 1U \u003c\u003c (page_shift - PAGE_SHIFT)) {\n-\t\tint err;\n-\n-\t\terr = vmap_range_noflush(addr, addr + (1UL \u003c\u003c page_shift),\n+\t\t\tpage_shift == PAGE_SHIFT) {\n+\t\terr = vmap_small_pages_range_noflush(addr, end, prot, pages);\n+\t} else {\n+\t\tfor (i = 0; i \u003c nr; i += 1U \u003c\u003c (page_shift - PAGE_SHIFT)) {\n+\t\t\terr = vmap_range_noflush(addr, addr + (1UL \u003c\u003c page_shift),\n \t\t\t\t\tpage_to_phys(pages[i]), prot,\n \t\t\t\t\tpage_shift);\n-\t\tif (err)\n-\t\t\treturn err;\n+\t\t\tif (err)\n+\t\t\t\tbreak;\n \n-\t\taddr += 1UL \u003c\u003c page_shift;\n+\t\t\taddr += 1UL \u003c\u003c page_shift;\n+\t\t}\n \t}\n \n-\treturn 0;\n+\t/* Undo the PTEs installed before the failure. */\n+\tif (err)\n+\t\t__vunmap_range_noflush(start, end);\n+\n+\treturn err;\n }\n \n int vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n@@ -715,7 +726,16 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n \n \tif (ret)\n \t\treturn ret;\n-\treturn __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);\n+\n+\tret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);\n+\t/*\n+\t * The page tables undo themselves on failure. Tear down the\n+\t * metadata that was fully set up before the mapping failed.\n+\t */\n+\tif (ret)\n+\t\tkmsan_vunmap_range_noflush(addr, end);\n+\n+\treturn ret;\n }\n \n static int __vmap_pages_range(unsigned long addr, unsigned long end,\n"
} |
| 2/1 | 2026/10/09 09:33 | agent | patch-evaluator |
4mModel:core Args: null Results: {
"EnableConfigs": null,
"FocusSymbols": [
"__vmap_pages_range_noflush",
"vmap_pages_range_noflush",
"vmap_page_range",
"kmsan_vmap_pages_range_noflush"
],
"Reasoning": "The patch alters core memory management code in mm/vmalloc.c, mm/percpu-vm.c, and mm/kmsan/shadow.c. It introduces new runtime assertions (WARN_ON_ONCE checks on address bounds and page shift) in __vmap_pages_range_noflush() and modifies error unwinding semantics so that partial page table mappings roll back automatically on failure across vmap_page_range(), __vmap_pages_range_noflush(), and kmsan_vmap_pages_range_noflush(). These code paths are reachable on amd64 in virtualized environments via standard vmalloc, vmap, and percpu allocations.",
"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 3eeb0ec9d1278ab64da2fcb0f06e870d40cc97bc
Author: syz-cluster <triage@syzkaller.com>
Date: Fri Oct 9 09:33:29 2026 +0000
syz-cluster: applied patch under review
diff --git a/arch/powerpc/kernel/isa-bridge.c b/arch/powerpc/kernel/isa-bridge.c
index 5c064485197a9..93029d85e6eaf 100644
--- a/arch/powerpc/kernel/isa-bridge.c
+++ b/arch/powerpc/kernel/isa-bridge.c
@@ -46,9 +46,8 @@ static void remap_isa_base(phys_addr_t pa, unsigned long size)
WARN_ON_ONCE(size & ~PAGE_MASK);
if (slab_is_available()) {
- if (vmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,
- pgprot_noncached(PAGE_KERNEL)))
- vunmap_range(ISA_IO_BASE, ISA_IO_BASE + size);
+ vmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,
+ pgprot_noncached(PAGE_KERNEL));
} else {
early_ioremap_range(ISA_IO_BASE, pa, size,
pgprot_noncached(PAGE_KERNEL));
diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
index e27342ef128b8..f74269636d5ec 100644
--- a/arch/powerpc/kernel/pci_64.c
+++ b/arch/powerpc/kernel/pci_64.c
@@ -139,10 +139,8 @@ void __iomem *ioremap_phb(phys_addr_t paddr, unsigned long size)
addr = (unsigned long)area->addr;
if (ioremap_page_range(addr, addr + size, paddr,
- pgprot_noncached(PAGE_KERNEL))) {
- vunmap_range(addr, addr + size);
+ pgprot_noncached(PAGE_KERNEL)))
return NULL;
- }
return (void __iomem *)addr;
}
diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
index 0c88d89bf0d68..2166086d3dc3b 100644
--- a/mm/kmsan/shadow.c
+++ b/mm/kmsan/shadow.c
@@ -258,6 +258,10 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
o_pages, page_shift);
kmsan_leave_runtime();
if (mapped) {
+ /* Undo the shadow mapping set up above. */
+ kmsan_enter_runtime();
+ __vunmap_range_noflush(shadow_start, shadow_end);
+ kmsan_leave_runtime();
err = mapped;
goto ret;
}
diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
index 509d8901835cd..59d3a336a6bd1 100644
--- a/mm/percpu-vm.c
+++ b/mm/percpu-vm.c
@@ -252,10 +252,11 @@ static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,
return 0;
err:
for_each_possible_cpu(tcpu) {
- __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
- page_end - page_start);
+ /* The failing CPU's partial mapping undoes itself */
if (tcpu == cpu)
break;
+ __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
+ page_end - page_start);
}
pcpu_post_unmap_tlb_flush(chunk, page_start, page_end);
return err;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index db669103dc666..e1b376f57dd25 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -363,6 +363,9 @@ int vmap_page_range(unsigned long addr, unsigned long end,
if (!err)
err = kmsan_ioremap_page_range(addr, end, phys_addr, prot,
ioremap_max_page_shift);
+ if (err)
+ __vunmap_range_noflush(addr, end);
+
return err;
}
@@ -683,27 +686,35 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
pgprot_t prot, struct page **pages, unsigned int page_shift)
{
unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
+ unsigned long start = addr;
+ int err = 0;
+
+ if (WARN_ON_ONCE(addr >= end))
+ return -EINVAL;
if (WARN_ON_ONCE(page_shift < PAGE_SHIFT))
return -EINVAL;
if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
- page_shift == PAGE_SHIFT)
- return vmap_small_pages_range_noflush(addr, end, prot, pages);
-
- for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
- int err;
-
- err = vmap_range_noflush(addr, addr + (1UL << page_shift),
+ page_shift == PAGE_SHIFT) {
+ err = vmap_small_pages_range_noflush(addr, end, prot, pages);
+ } else {
+ for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
+ err = vmap_range_noflush(addr, addr + (1UL << page_shift),
page_to_phys(pages[i]), prot,
page_shift);
- if (err)
- return err;
+ if (err)
+ break;
- addr += 1UL << page_shift;
+ addr += 1UL << page_shift;
+ }
}
- return 0;
+ /* Undo the PTEs installed before the failure. */
+ if (err)
+ __vunmap_range_noflush(start, end);
+
+ return err;
}
int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
@@ -715,7 +726,16 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
if (ret)
return ret;
- return __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+
+ ret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+ /*
+ * The page tables undo themselves on failure. Tear down the
+ * metadata that was fully set up before the mapping failed.
+ */
+ if (ret)
+ kmsan_vunmap_range_noflush(addr, end);
+
+ return ret;
}
static int __vmap_pages_range(unsigned long addr, unsigned long end,
|
| 3/2 | 2026/10/09 09:33 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 4794 output: 34 thoughts: 233 Thoughts: **Analyzing this Patch: A Core Memory Subsystem Deep Dive** Okay, let's break this down. First, I need to understand the scope. I see a patch hitting a few files. Now, some of these, like `arch/powerpc/kernel/isa-bridge.c` and `arch/powerpc/kernel/pci_64.c`, are architecture-specific, specifically PowerPC, but the target here is amd64, so those are likely not relevant for understanding how it affects me. However, the other three files, `mm/kmsan/shadow.c`, `mm/percpu-vm.c`, and `mm/vmalloc.c`, that's where it gets interesting. These are core memory management components. Since the architecture is amd64, I need to focus on these core memory files. That likely means something in the vmalloc subsystem is changing, the percpu allocator, or some KMSAN shadow memory handling is being modified. I should use `read-file` or `grepper` to see the exact changes in the context of `mm/vmalloc.c` first. This should give me a good handle on the intent of the changes, and what possible side effects might occur. |
| 4/2 | 2026/10/09 09:33 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 355,
"LineCount": 25
}Results: {
"Contents": " 355:\tint vmap_page_range(unsigned long addr, unsigned long end,\n 356:\t\t\t phys_addr_t phys_addr, pgprot_t prot)\n 357:\t{\n 358:\t\tint err;\n 359:\t\n 360:\t\terr = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot),\n 361:\t\t\t\t\t ioremap_max_page_shift);\n 362:\t\tflush_cache_vmap(addr, end);\n 363:\t\tif (!err)\n 364:\t\t\terr = kmsan_ioremap_page_range(addr, end, phys_addr, prot,\n 365:\t\t\t\t\t\t ioremap_max_page_shift);\n 366:\t\tif (err)\n 367:\t\t\t__vunmap_range_noflush(addr, end);\n 368:\t\n 369:\t\treturn err;\n 370:\t}\n 371:\t\n 372:\tint ioremap_page_range(unsigned long addr, unsigned long end,\n 373:\t\t\tphys_addr_t phys_addr, pgprot_t prot)\n 374:\t{\n 375:\t\tstruct vm_struct *area;\n 376:\t\n 377:\t\tarea = find_vm_area((void *)addr);\n 378:\t\tif (!area || !(area-\u003eflags \u0026 VM_IOREMAP)) {\n 379:\t\t\tWARN_ONCE(1, \"vm_area at addr %lx is not marked as VM_IOREMAP\\n\", addr);\n"
} |
| 5/2 | 2026/10/09 09:33 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 5749 output: 34 thoughts: 25 Thoughts: Okay, let's dive into this. Here's my thought process on dissecting `__vmap_pages_range_noflush` in `mm/vmalloc.c`, as if I were working through it: **Analyzing `__vmap_pages_range_noflush` in `mm/vmalloc.c`** Right, let's get down to brass tacks. I'm focusing on `__vmap_pages_range_noflush` – that immediately tells me we're dealing with a core vmalloc function, one concerned with mapping pages into the virtual address space. The "noflush" suffix is the key here; it signals that we're bypassing some kind of cache coherency or TLB invalidation step. That's immediately interesting – performance optimization, potentially, but also a point that demands careful attention to ensure data integrity and avoid obscure bugs. My initial questions are: What's the context? What calls this function? And, most importantly, *why* are we bypassing the flush? Is this part of a larger vmalloc optimization strategy? Is it used for special memory regions, or during early boot, or something similar? I need to trace the call paths to understand the rationale and potential risks. Any place where we're trading cache coherency for speed immediately demands deeper scrutiny. I'll need to understand the data structures and control flow intimately to evaluate the implications of this design choice. I suspect we will be seeing some tricks with page tables and address spaces. This could be a complex situation that requires careful testing. |
| 6/2 | 2026/10/09 09:33 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 680,
"LineCount": 65
}Results: {
"Contents": " 680:\t * The caller is responsible for calling flush_cache_vmap() after this\n 681:\t * function returns successfully and before the addresses are accessed.\n 682:\t *\n 683:\t * This is an internal function only. Do not use outside mm/.\n 684:\t */\n 685:\tint __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n 686:\t\t\tpgprot_t prot, struct page **pages, unsigned int page_shift)\n 687:\t{\n 688:\t\tunsigned int i, nr = (end - addr) \u003e\u003e PAGE_SHIFT;\n 689:\t\tunsigned long start = addr;\n 690:\t\tint err = 0;\n 691:\t\n 692:\t\tif (WARN_ON_ONCE(addr \u003e= end))\n 693:\t\t\treturn -EINVAL;\n 694:\t\n 695:\t\tif (WARN_ON_ONCE(page_shift \u003c PAGE_SHIFT))\n 696:\t\t\treturn -EINVAL;\n 697:\t\n 698:\t\tif (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||\n 699:\t\t\t\tpage_shift == PAGE_SHIFT) {\n 700:\t\t\terr = vmap_small_pages_range_noflush(addr, end, prot, pages);\n 701:\t\t} else {\n 702:\t\t\tfor (i = 0; i \u003c nr; i += 1U \u003c\u003c (page_shift - PAGE_SHIFT)) {\n 703:\t\t\t\terr = vmap_range_noflush(addr, addr + (1UL \u003c\u003c page_shift),\n 704:\t\t\t\t\t\tpage_to_phys(pages[i]), prot,\n 705:\t\t\t\t\t\tpage_shift);\n 706:\t\t\t\tif (err)\n 707:\t\t\t\t\tbreak;\n 708:\t\n 709:\t\t\t\taddr += 1UL \u003c\u003c page_shift;\n 710:\t\t\t}\n 711:\t\t}\n 712:\t\n 713:\t\t/* Undo the PTEs installed before the failure. */\n 714:\t\tif (err)\n 715:\t\t\t__vunmap_range_noflush(start, end);\n 716:\t\n 717:\t\treturn err;\n 718:\t}\n 719:\t\n 720:\tint vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n 721:\t\t\tpgprot_t prot, struct page **pages, unsigned int page_shift,\n 722:\t\t\tgfp_t gfp_mask)\n 723:\t{\n 724:\t\tint ret = kmsan_vmap_pages_range_noflush(addr, end, prot, pages,\n 725:\t\t\t\t\t\t\tpage_shift, gfp_mask);\n 726:\t\n 727:\t\tif (ret)\n 728:\t\t\treturn ret;\n 729:\t\n 730:\t\tret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);\n 731:\t\t/*\n 732:\t\t * The page tables undo themselves on failure. Tear down the\n 733:\t\t * metadata that was fully set up before the mapping failed.\n 734:\t\t */\n 735:\t\tif (ret)\n 736:\t\t\tkmsan_vunmap_range_noflush(addr, end);\n 737:\t\n 738:\t\treturn ret;\n 739:\t}\n 740:\t\n 741:\tstatic int __vmap_pages_range(unsigned long addr, unsigned long end,\n 742:\t\t\tpgprot_t prot, struct page **pages, unsigned int page_shift,\n 743:\t\t\tgfp_t gfp_mask)\n 744:\t{\n"
} |
| 7/2 | 2026/10/09 09:33 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 7130 output: 25 thoughts: 26 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: **Investigating `vmap_small_pages_range_noflush`** Okay, let's dive into this `vmap_small_pages_range_noflush` function. It’s been popping up in my research, and I need to solidify my understanding of it. My first priority is locating it within the relevant codebase. I need to know where it's defined and called. Is it a core kernel function, part of a specific subsystem, or maybe a module? Once I have its definition, I'll need to meticulously analyze its implementation. What's its primary role? From the name, I'm inferring it deals with virtual memory mapping, potentially with smaller page sizes and without immediate cache flushes. But I need to confirm those assumptions, and identify the subtle nuances. What are the specific memory regions it operates on? How does it interact with the page tables and the TLB? Does it have any implications for performance, security, or concurrency? Are there any associated locking mechanisms? I'll also be watching for the likely `VM_NOFLUSH` flag, which hints that this function is involved with lazy flushing of TLB entries. I'll be paying close attention to any error handling or boundary checks within the function. What are the potential failure scenarios, and how are they managed? Are there any known vulnerabilities associated with its usage? And what are the performance characteristics? Are there any scenarios in which using this function could lead to performance bottlenecks or other issues. Ultimately, I need a complete mental map of its functionality and how it affects the system. |
| 8/2 | 2026/10/09 09:33 | tool | grepper |
0mArgs:{
"Expression": "vmap_small_pages_range_noflush"
}Results: {
"Output": "mm/vmalloc.c=631=static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr,\n--\nmm/vmalloc.c-648-\nmm/vmalloc.c:649:static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.c-650-\t\tpgprot_t prot, struct page **pages)\n--\nmm/vmalloc.c=685=int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-699-\t\t\tpage_shift == PAGE_SHIFT) {\nmm/vmalloc.c:700:\t\terr = vmap_small_pages_range_noflush(addr, end, prot, pages);\nmm/vmalloc.c-701-\t} else {\n"
} |
| 9/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 7759 output: 34 thoughts: 17 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: **Analyzing `vmap_small_pages_range_noflush`** Alright, let's dive into `vmap_small_pages_range_noflush`. Immediately, the name suggests some key aspects of its function. "Vmap" implies we're dealing with virtual memory mapping, probably for kernel-level allocations. "Small pages" is interesting; this likely means we're *not* talking about Huge Pages, but rather standard page sizes, hinting at the potential for more fine-grained control or lower overhead compared to huge page allocations. The "range" part means we're mapping a contiguous area of virtual address space, a common requirement. And then, crucially, "noflush." That last bit is the real clue. "Noflush" strongly implies that this function operates with some degree of cache coherency in mind, which is a major factor in performance. Specifically, the "noflush" part tells me that this particular mapping is optimized to avoid some kind of flush operation; possibly writeback flushes or invalidation flushes. Given that these are my initial reactions, I expect to be seeing some sort of optimized mapping. The function's internal architecture must be designed to avoid any unnecessary cache operations, like TLB shootdowns. I'm already anticipating questions: What are the conditions that allow a "noflush" approach? Under what scenarios is this the right strategy? Are there any tradeoffs in terms of data consistency or performance elsewhere in the system? And of course, how does it all interact with the underlying hardware's cache mechanisms and the memory management unit? Let's take a closer look and dissect this implementation. |
| 10/2 | 2026/10/09 09:34 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 645,
"LineCount": 40
}Results: {
"Contents": " 645:\t\t} while (p4d++, addr = next, addr != end);\n 646:\t\treturn 0;\n 647:\t}\n 648:\t\n 649:\tstatic int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\n 650:\t\t\tpgprot_t prot, struct page **pages)\n 651:\t{\n 652:\t\tunsigned long start = addr;\n 653:\t\tpgd_t *pgd;\n 654:\t\tunsigned long next;\n 655:\t\tint err = 0;\n 656:\t\tint nr = 0;\n 657:\t\tpgtbl_mod_mask mask = 0;\n 658:\t\n 659:\t\tBUG_ON(addr \u003e= end);\n 660:\t\tpgd = pgd_offset_k(addr);\n 661:\t\tdo {\n 662:\t\t\tnext = pgd_addr_end(addr, end);\n 663:\t\t\tif (pgd_bad(*pgd))\n 664:\t\t\t\tmask |= PGTBL_PGD_MODIFIED;\n 665:\t\t\terr = vmap_pages_p4d_range(pgd, addr, next, prot, pages, \u0026nr, \u0026mask);\n 666:\t\t\tif (err)\n 667:\t\t\t\tbreak;\n 668:\t\t} while (pgd++, addr = next, addr != end);\n 669:\t\n 670:\t\tif (mask \u0026 ARCH_PAGE_TABLE_SYNC_MASK)\n 671:\t\t\tarch_sync_kernel_mappings(start, end);\n 672:\t\n 673:\t\treturn err;\n 674:\t}\n 675:\t\n 676:\t/*\n 677:\t * vmap_pages_range_noflush is similar to vmap_pages_range, but does not\n 678:\t * flush caches.\n 679:\t *\n 680:\t * The caller is responsible for calling flush_cache_vmap() after this\n 681:\t * function returns successfully and before the addresses are accessed.\n 682:\t *\n 683:\t * This is an internal function only. Do not use outside mm/.\n 684:\t */\n"
} |
| 11/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 8775 output: 36 thoughts: 909 Thoughts: **Analyzing the Error Handling in VM Mapping Functions** Okay, let's break down this change in error handling across these vmap functions. It seems they've introduced a consistent mechanism for undoing partially completed mappings when something goes wrong. My initial thought is to check how `vmap_small_pages_range_noflush` now handles errors. Previously, it simply returned the error code. Now, if it fails (or if the loop in the "else" condition, handling huge pages, fails), it calls `__vunmap_range_noflush(start, end)`. This immediately tells me that they're aiming for a rollback, ensuring a consistent state. It makes total sense - we don't want a partially mapped region if something errors out during the process. We're also checking how `vmap_pages_range_noflush` is handled, and noticing a similar `kmsan_vunmap_range_noflush` call in the event of failure to tear down metadata. The same pattern is present in `vmap_page_range` where it calls `__vunmap_range_noflush(addr, end)` on failure, providing a clear indication of unmapping. It looks like the `kmsan` module also calls `__vunmap_range_noflush` in the event of mapping failure as well. This makes sense from a resource cleanup perspective, but it's important to understand *why* this is happening in `kmsan` as this is not a mapping function and appears to be shadow mapping as well. Now, let's look at `mm/percpu-vm.c`. The error handling in the per-cpu VM also involves undoing partial mappings. If there's an error, the code iterates through other CPUs and unmaps their portions of the mapping using `__pcpu_unmap_pages` before flushing the TLB with `pcpu_post_unmap_tlb_flush`. This is an efficient and proper method to unmap each CPU after an error. The failing CPU's partial mapping undoes itself, so that's nice. Essentially, they've implemented a robust error recovery strategy for vmap-related functions. It's good to see this level of careful error handling and cleanup, as it prevents memory leaks and inconsistent states within the kernel. |
| 12/2 | 2026/10/09 09:34 | tool | read-file |
0mArgs:{
"File": "mm/percpu-vm.c",
"FirstLine": 220,
"LineCount": 45
}Results: {
"Contents": " 220:\t/**\n 221:\t * pcpu_map_pages - map pages into a pcpu_chunk\n 222:\t * @chunk: chunk of interest\n 223:\t * @pages: pages array containing pages to be mapped\n 224:\t * @page_start: page index of the first page to map\n 225:\t * @page_end: page index of the last page to map + 1\n 226:\t * @gfp: allocation flags passed to the underlying allocator\n 227:\t *\n 228:\t * For each cpu, map pages [@page_start,@page_end) into @chunk. The\n 229:\t * caller is responsible for calling pcpu_post_map_flush() after all\n 230:\t * mappings are complete.\n 231:\t *\n 232:\t * This function is responsible for setting up whatever is necessary for\n 233:\t * reverse lookup (addr -\u003e chunk).\n 234:\t */\n 235:\tstatic int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,\n 236:\t\t\t\t int page_start, int page_end, gfp_t gfp)\n 237:\t{\n 238:\t\tunsigned int cpu, tcpu;\n 239:\t\tint i, err;\n 240:\t\n 241:\t\tfor_each_possible_cpu(cpu) {\n 242:\t\t\terr = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),\n 243:\t\t\t\t\t \u0026pages[pcpu_page_idx(cpu, page_start)],\n 244:\t\t\t\t\t page_end - page_start, gfp);\n 245:\t\t\tif (err \u003c 0)\n 246:\t\t\t\tgoto err;\n 247:\t\n 248:\t\t\tfor (i = page_start; i \u003c page_end; i++)\n 249:\t\t\t\tpcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],\n 250:\t\t\t\t\t\t chunk);\n 251:\t\t}\n 252:\t\treturn 0;\n 253:\terr:\n 254:\t\tfor_each_possible_cpu(tcpu) {\n 255:\t\t\t/* The failing CPU's partial mapping undoes itself */\n 256:\t\t\tif (tcpu == cpu)\n 257:\t\t\t\tbreak;\n 258:\t\t\t__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),\n 259:\t\t\t\t\t page_end - page_start);\n 260:\t\t}\n 261:\t\tpcpu_post_unmap_tlb_flush(chunk, page_start, page_end);\n 262:\t\treturn err;\n 263:\t}\n 264:\t\n"
} |
| 13/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 10960 output: 21 thoughts: 16 Thoughts: Here's a summary of my thought process: **Diving into `__pcpu_map_pages`** Okay, so I'm digging into `__pcpu_map_pages`. The goal here is to understand the context and implications of this function call. I need to figure out *what* it's calling. Understanding the lower-level functions that `__pcpu_map_pages` relies on is crucial to seeing the bigger picture. I'm going to follow the call chain and get a feel for how the function is used. Let's see what the subsequent functions might show. |
| 14/2 | 2026/10/09 09:34 | tool | grepper |
0mArgs:{
"Expression": "__pcpu_map_pages"
}Results: {
"Output": "mm/percpu-vm.c=193=static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,\n--\nmm/percpu-vm.c-200-\nmm/percpu-vm.c:201:static int __pcpu_map_pages(unsigned long addr, struct page **pages,\nmm/percpu-vm.c-202-\t\t\t int nr_pages, gfp_t gfp)\n--\nmm/percpu-vm.c=235=static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,\n--\nmm/percpu-vm.c-241-\tfor_each_possible_cpu(cpu) {\nmm/percpu-vm.c:242:\t\terr = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),\nmm/percpu-vm.c-243-\t\t\t\t \u0026pages[pcpu_page_idx(cpu, page_start)],\n--\nmm/percpu.c=3197=int __init pcpu_page_first_chunk(size_t reserved_size, pcpu_fc_cpu_to_node_fn_t cpu_to_nd_fn)\n--\nmm/percpu.c-3260-\t\t/* pte already populated, the following shouldn't fail */\nmm/percpu.c:3261:\t\trc = __pcpu_map_pages(unit_addr, \u0026pages[unit * unit_pages],\nmm/percpu.c-3262-\t\t\t\t unit_pages, GFP_KERNEL);\n"
} |
| 15/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 11535 output: 36 thoughts: 24 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving into `__pcpu_map_pages`** Right, let's pull up the source code for `__pcpu_map_pages` in `mm/percpu-vm.c`. I need to get a clear picture of how this function handles the mapping of pages for per-CPU variables. This function is critical for understanding the mechanics of per-CPU allocation and management within the kernel's memory management subsystem, so I want a deep dive. I'm especially interested in the nuances of its interactions with the page tables, and how it handles potential NUMA effects. I'll be looking for how it secures the memory that is being allocated for a variety of tasks. |
| 16/2 | 2026/10/09 09:34 | tool | read-file |
0mArgs:{
"File": "mm/percpu-vm.c",
"FirstLine": 200,
"LineCount": 25
}Results: {
"Contents": " 200:\t\n 201:\tstatic int __pcpu_map_pages(unsigned long addr, struct page **pages,\n 202:\t\t\t\t int nr_pages, gfp_t gfp)\n 203:\t{\n 204:\t\tunsigned int flags;\n 205:\t\tint ret;\n 206:\t\n 207:\t\t/*\n 208:\t\t * The vmalloc page table allocation path does not pass @gfp down\n 209:\t\t * explicitly. Apply the corresponding memalloc scope so implicit\n 210:\t\t * page table allocations preserve NOFS/NOIO constraints.\n 211:\t\t */\n 212:\t\tflags = memalloc_apply_gfp_scope(gfp);\n 213:\t\tret = vmap_pages_range_noflush(addr, addr + (nr_pages \u003c\u003c PAGE_SHIFT),\n 214:\t\t\t\t\t PAGE_KERNEL, pages, PAGE_SHIFT, gfp);\n 215:\t\tmemalloc_restore_scope(flags);\n 216:\t\n 217:\t\treturn ret;\n 218:\t}\n 219:\t\n 220:\t/**\n 221:\t * pcpu_map_pages - map pages into a pcpu_chunk\n 222:\t * @chunk: chunk of interest\n 223:\t * @pages: pages array containing pages to be mapped\n 224:\t * @page_start: page index of the first page to map\n"
} |
| 17/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12144 output: 24 thoughts: 150 Thoughts: **Analyzing the Kernel's Page Mapping Logic** Okay, so I'm digging into this kernel code and things are becoming clearer. It looks like `__pcpu_map_pages` relies on `vmap_pages_range_noflush`, which in turn, calls `__vmap_pages_range_noflush`. Interesting. And, from what I'm seeing, `__vmap_pages_range_noflush` now *unmaps* pages if it hits an error. That's a key detail! It wasn't always this way. Previously, `vmap_pages_range_noflush` or `__vmap_pages_range_noflush` didn't clean up the Page Table Entries (PTEs) when they failed. The callers, i.e. the functions that call `__vmap_pages_range_noflush`, were responsible for handling that mess. Now, let's figure out *why* this change happened. I need to understand the motivation behind this patch. Let me check the git log and the commit message for more context. Hopefully the commit message explains the rationale! |
| 18/2 | 2026/10/09 09:34 | tool | grepper |
0mArgs:{
"Expression": "The failing CPU's partial mapping undoes itself"
}Results: {
"Output": "mm/percpu-vm.c=235=static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,\n--\nmm/percpu-vm.c-254-\tfor_each_possible_cpu(tcpu) {\nmm/percpu-vm.c:255:\t\t/* The failing CPU's partial mapping undoes itself */\nmm/percpu-vm.c-256-\t\tif (tcpu == cpu)\n"
} |
| 19/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12685 output: 23 thoughts: 63 Thoughts: Okay, let's see what's going on here. First, my instinct is to quickly check the recent commit history for context. If I had direct access, I'd immediately fire up `git log -n 5` or something comparable. However, since I don't, I need to work with what's available which seems to be the commit diff. Fine. Now, moving on, the core of the issue likely involves `__vunmap_range_noflush`. My next step is to understand precisely what that function does and how it's defined within this system. I need to get a clear picture of its behavior to effectively diagnose or address the underlying problem. Time to dig in and understand this core function. |
| 20/2 | 2026/10/09 09:34 | tool | grepper |
0mArgs:{
"Expression": "__vunmap_range_noflush"
}Results: {
"Output": "mm/kmsan/hooks.c=139=void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)\nmm/kmsan/hooks.c-140-{\nmm/kmsan/hooks.c:141:\t__vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end));\nmm/kmsan/hooks.c:142:\t__vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end));\nmm/kmsan/hooks.c-143-\tflush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));\n--\nmm/kmsan/hooks.c=149=static void kmsan_iounmap_pages(unsigned long start, unsigned long end)\n--\nmm/kmsan/hooks.c-170-\t}\nmm/kmsan/hooks.c:171:\t__vunmap_range_noflush(shadow_start, shadow_end);\nmm/kmsan/hooks.c:172:\t__vunmap_range_noflush(origin_start, origin_end);\nmm/kmsan/hooks.c-173-\tflush_tlb_kernel_range(shadow_start, shadow_end);\n--\nmm/kmsan/shadow.c=217=int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,\n--\nmm/kmsan/shadow.c-262-\t\tkmsan_enter_runtime();\nmm/kmsan/shadow.c:263:\t\t__vunmap_range_noflush(shadow_start, shadow_end);\nmm/kmsan/shadow.c-264-\t\tkmsan_leave_runtime();\n--\nmm/vmalloc.c=355=int vmap_page_range(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-366-\tif (err)\nmm/vmalloc.c:367:\t\t__vunmap_range_noflush(addr, end);\nmm/vmalloc.c-368-\n--\nmm/vmalloc.c=475=static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-506- */\nmm/vmalloc.c:507:void __vunmap_range_noflush(unsigned long start, unsigned long end)\nmm/vmalloc.c-508-{\n--\nmm/vmalloc.c=529=void vunmap_range_noflush(unsigned long start, unsigned long end)\n--\nmm/vmalloc.c-531-\tkmsan_vunmap_range_noflush(start, end);\nmm/vmalloc.c:532:\t__vunmap_range_noflush(start, end);\nmm/vmalloc.c-533-}\n--\nmm/vmalloc.c=685=int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-714-\tif (err)\nmm/vmalloc.c:715:\t\t__vunmap_range_noflush(start, end);\nmm/vmalloc.c-716-\n--\nmm/vmalloc.h=45=void vunmap_range_noflush(unsigned long start, unsigned long end);\nmm/vmalloc.h-46-\nmm/vmalloc.h:47:void __vunmap_range_noflush(unsigned long start, unsigned long end);\nmm/vmalloc.h-48-\n"
} |
| 21/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 13831 output: 23 thoughts: 24 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Analyzing the `__vmap_pages_range_noflush` Callers** Alright, time to dig in. I need to get a clear picture of how `__vmap_pages_range_noflush` is being used. Specifically, I want to understand the *callers* of this function. I need to trace the call paths to get a sense of the contexts where it's being invoked. What are the calling sequences? What are the calling conventions used? Is it being called within tight loops? Are any locks held? Knowing this will be key to understanding its overall impact and any potential bottlenecks or areas for optimization. This analysis should help me to understand the calling patterns. |
| 22/2 | 2026/10/09 09:34 | tool | grepper |
0mArgs:{
"Expression": "vmap_pages_range_noflush"
}Results: {
"Output": "include/linux/kmsan.h=127=void kmsan_kfree_large(const void *ptr);\n--\ninclude/linux/kmsan.h-141- */\ninclude/linux/kmsan.h:142:int __must_check kmsan_vmap_pages_range_noflush(unsigned long start,\ninclude/linux/kmsan.h-143-\t\t\t\t\t\tunsigned long end,\n--\ninclude/linux/kmsan.h=346=static inline void kmsan_kfree_large(const void *ptr)\n--\ninclude/linux/kmsan.h-349-\ninclude/linux/kmsan.h:350:static inline int __must_check kmsan_vmap_pages_range_noflush(\ninclude/linux/kmsan.h-351-\tunsigned long start, unsigned long end, pgprot_t prot,\n--\nmm/kmsan/hooks.c=182=int kmsan_ioremap_page_range(unsigned long start, unsigned long end,\n--\nmm/kmsan/hooks.c-203-\t\t}\nmm/kmsan/hooks.c:204:\t\tmapped = __vmap_pages_range_noflush(\nmm/kmsan/hooks.c-205-\t\t\tvmalloc_shadow(start + off),\n--\nmm/kmsan/hooks.c-213-\t\tmapped_end = start + off + PAGE_SIZE;\nmm/kmsan/hooks.c:214:\t\tmapped = __vmap_pages_range_noflush(\nmm/kmsan/hooks.c-215-\t\t\tvmalloc_origin(start + off),\n--\nmm/kmsan/shadow.c=206=void kmsan_free_page(struct page *page, unsigned int order)\n--\nmm/kmsan/shadow.c-216-\nmm/kmsan/shadow.c:217:int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,\nmm/kmsan/shadow.c-218-\t\t\t\t pgprot_t prot, struct page **pages,\n--\nmm/kmsan/shadow.c-248-\tkmsan_enter_runtime();\nmm/kmsan/shadow.c:249:\tmapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,\nmm/kmsan/shadow.c-250-\t\t\t\t\t s_pages, page_shift);\n--\nmm/kmsan/shadow.c-256-\tkmsan_enter_runtime();\nmm/kmsan/shadow.c:257:\tmapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,\nmm/kmsan/shadow.c-258-\t\t\t\t\t o_pages, page_shift);\n--\nmm/percpu-vm.c=201=static int __pcpu_map_pages(unsigned long addr, struct page **pages,\n--\nmm/percpu-vm.c-212-\tflags = memalloc_apply_gfp_scope(gfp);\nmm/percpu-vm.c:213:\tret = vmap_pages_range_noflush(addr, addr + (nr_pages \u003c\u003c PAGE_SHIFT),\nmm/percpu-vm.c-214-\t\t\t\t PAGE_KERNEL, pages, PAGE_SHIFT, gfp);\n--\nmm/vmalloc.c=649=static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-676-/*\nmm/vmalloc.c:677: * vmap_pages_range_noflush is similar to vmap_pages_range, but does not\nmm/vmalloc.c-678- * flush caches.\n--\nmm/vmalloc.c-684- */\nmm/vmalloc.c:685:int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.c-686-\t\tpgprot_t prot, struct page **pages, unsigned int page_shift)\n--\nmm/vmalloc.c-719-\nmm/vmalloc.c:720:int vmap_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.c-721-\t\tpgprot_t prot, struct page **pages, unsigned int page_shift,\n--\nmm/vmalloc.c-723-{\nmm/vmalloc.c:724:\tint ret = kmsan_vmap_pages_range_noflush(addr, end, prot, pages,\nmm/vmalloc.c-725-\t\t\t\t\t\tpage_shift, gfp_mask);\n--\nmm/vmalloc.c-729-\nmm/vmalloc.c:730:\tret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);\nmm/vmalloc.c-731-\t/*\n--\nmm/vmalloc.c=741=static int __vmap_pages_range(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-746-\nmm/vmalloc.c:747:\terr = vmap_pages_range_noflush(addr, end, prot, pages, page_shift, gfp_mask);\nmm/vmalloc.c-748-\tflush_cache_vmap(addr, end);\n--\nmm/vmalloc.h=12=void __init vmalloc_init(void);\nmm/vmalloc.h:13:int __must_check vmap_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.h-14-\t\tpgprot_t prot, struct page **pages,\n--\nmm/vmalloc.h=20=static inline\nmm/vmalloc.h:21:int __must_check vmap_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.h-22-\t\tpgprot_t prot, struct page **pages,\n--\nmm/vmalloc.h=39=void clear_vm_uninitialized_flag(struct vm_struct *vm);\nmm/vmalloc.h-40-\nmm/vmalloc.h:41:int __must_check __vmap_pages_range_noflush(unsigned long addr,\nmm/vmalloc.h-42-\t\tunsigned long end, pgprot_t prot,\n"
} |
| 23/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 15620 output: 21 thoughts: 35 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: **Investigating `__vmap_pages_range` and `vmap_pages_range`** Right, let's dig into this. I need to understand the call hierarchy for `__vmap_pages_range` and `vmap_pages_range`. The core of any good memory management analysis starts with understanding how the key functions are *used*. So, first things first: I'm going to track down every instance where these functions are directly called. I need a clear map of the callers to get a proper handle on their purpose. This seems like a crucial step in tracing how memory is allocated and managed within this framework. This also informs the design. |
| 24/2 | 2026/10/09 09:34 | tool | grepper |
0mArgs:{
"Expression": "__vmap_pages_range"
}Results: {
"Output": "mm/kmsan/hooks.c=182=int kmsan_ioremap_page_range(unsigned long start, unsigned long end,\n--\nmm/kmsan/hooks.c-203-\t\t}\nmm/kmsan/hooks.c:204:\t\tmapped = __vmap_pages_range_noflush(\nmm/kmsan/hooks.c-205-\t\t\tvmalloc_shadow(start + off),\n--\nmm/kmsan/hooks.c-213-\t\tmapped_end = start + off + PAGE_SIZE;\nmm/kmsan/hooks.c:214:\t\tmapped = __vmap_pages_range_noflush(\nmm/kmsan/hooks.c-215-\t\t\tvmalloc_origin(start + off),\n--\nmm/kmsan/shadow.c=217=int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,\n--\nmm/kmsan/shadow.c-248-\tkmsan_enter_runtime();\nmm/kmsan/shadow.c:249:\tmapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,\nmm/kmsan/shadow.c-250-\t\t\t\t\t s_pages, page_shift);\n--\nmm/kmsan/shadow.c-256-\tkmsan_enter_runtime();\nmm/kmsan/shadow.c:257:\tmapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,\nmm/kmsan/shadow.c-258-\t\t\t\t\t o_pages, page_shift);\n--\nmm/vmalloc.c=649=static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-684- */\nmm/vmalloc.c:685:int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.c-686-\t\tpgprot_t prot, struct page **pages, unsigned int page_shift)\n--\nmm/vmalloc.c=720=int vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-729-\nmm/vmalloc.c:730:\tret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);\nmm/vmalloc.c-731-\t/*\n--\nmm/vmalloc.c-740-\nmm/vmalloc.c:741:static int __vmap_pages_range(unsigned long addr, unsigned long end,\nmm/vmalloc.c-742-\t\tpgprot_t prot, struct page **pages, unsigned int page_shift,\n--\nmm/vmalloc.c=764=int vmap_pages_range(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-766-{\nmm/vmalloc.c:767:\treturn __vmap_pages_range(addr, end, prot, pages, page_shift, GFP_KERNEL);\nmm/vmalloc.c-768-}\n--\nmm/vmalloc.c=3738=vm_area_alloc_pages(gfp_t gfp, int nid,\n--\nmm/vmalloc.c-3753-\t * pages. Do not attempt allocating smaller than order chunks since\nmm/vmalloc.c:3754:\t * __vmap_pages_range() expects physically contiguous pages of exactly\nmm/vmalloc.c-3755-\t * order long chunks.\n--\nmm/vmalloc.c=3935=static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,\n--\nmm/vmalloc.c-4012-\tdo {\nmm/vmalloc.c:4013:\t\tret = __vmap_pages_range(addr, addr + size, prot, area-\u003epages,\nmm/vmalloc.c-4014-\t\t\t\tpage_shift, nested_gfp);\n--\nmm/vmalloc.h=39=void clear_vm_uninitialized_flag(struct vm_struct *vm);\nmm/vmalloc.h-40-\nmm/vmalloc.h:41:int __must_check __vmap_pages_range_noflush(unsigned long addr,\nmm/vmalloc.h-42-\t\tunsigned long end, pgprot_t prot,\n"
} |
| 25/2 | 2026/10/09 09:34 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 16946 output: 23 thoughts: 116 Thoughts: Okay, let's break this down. **Diving into the Kernel's Virtual Mapping** Alright, so I'm seeing `__vmalloc_area_node()` making calls to `__vmap_pages_range()`. That's interesting, because `__vmap_pages_range()` then calls `vmap_pages_range_noflush()`, which further drills down into `__vmap_pages_range_noflush()`. Immediately, I recognize `__vmalloc_area_node()` as a core function used by *many* allocation functions like `vmalloc()`, `vzalloc()`, `vmap()` and the like. This suggests the foundation for virtual memory mapping within the kernel is built upon this specific chain of calls. But now my brain is pinging. I need to understand the full scope. I wonder, what *else* is using `vmap_pages_range()`? It's crucial to know all the calling contexts. A quick grep of the codebase should illuminate the connections, giving me a broader picture of where this function comes into play. Let's see what else relies on this vital function. |
| 26/2 | 2026/10/09 09:35 | tool | grepper |
0mArgs:{
"Expression": "\\bvmap_pages_range\\b"
}Results: {
"Output": "include/linux/vmalloc.h=230=extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,\n--\ninclude/linux/vmalloc.h-232-\ninclude/linux/vmalloc.h:233:int vmap_pages_range(unsigned long addr, unsigned long end, pgprot_t prot,\ninclude/linux/vmalloc.h-234-\t\t struct page **pages, unsigned int page_shift);\n--\nkernel/liveupdate/kexec_handover.c=1443=void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)\n--\nkernel/liveupdate/kexec_handover.c-1506-\tsize = get_vm_area_size(area);\nkernel/liveupdate/kexec_handover.c:1507:\terr = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);\nkernel/liveupdate/kexec_handover.c-1508-\tif (err)\n--\nmm/alloc_tag.c=777=static int vm_module_tags_populate(void)\n--\nmm/alloc_tag.c-802-\t\tif (nr \u003c more_pages ||\nmm/alloc_tag.c:803:\t\t vmap_pages_range(phys_end, phys_end + (nr \u003c\u003c PAGE_SHIFT), PAGE_KERNEL,\nmm/alloc_tag.c-804-\t\t\t\t next_page, PAGE_SHIFT) \u003c 0) {\n--\nmm/vmalloc.c=649=static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-676-/*\nmm/vmalloc.c:677: * vmap_pages_range_noflush is similar to vmap_pages_range, but does not\nmm/vmalloc.c-678- * flush caches.\n--\nmm/vmalloc.c=741=static int __vmap_pages_range(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-752-/**\nmm/vmalloc.c:753: * vmap_pages_range - map pages to a kernel virtual address\nmm/vmalloc.c-754- * @addr: start of the VM area to map\n--\nmm/vmalloc.c-763- */\nmm/vmalloc.c:764:int vmap_pages_range(unsigned long addr, unsigned long end,\nmm/vmalloc.c-765-\t\tpgprot_t prot, struct page **pages, unsigned int page_shift)\n--\nmm/vmalloc.c=795=int vm_area_map_pages(struct vm_struct *area, unsigned long start,\n--\nmm/vmalloc.c-803-\nmm/vmalloc.c:804:\treturn vmap_pages_range(start, end, PAGE_KERNEL, pages, PAGE_SHIFT);\nmm/vmalloc.c-805-}\n--\nmm/vmalloc.c=3150=void *vm_map_ram(struct page **pages, unsigned int count, int node)\n--\nmm/vmalloc.c-3173-\nmm/vmalloc.c:3174:\tif (vmap_pages_range(addr, addr + size, PAGE_KERNEL,\nmm/vmalloc.c-3175-\t\t\t\tpages, PAGE_SHIFT) \u003c 0) {\n--\nmm/vmalloc.c=3629=void *vmap(struct page **pages, unsigned int count,\n--\nmm/vmalloc.c-3656-\taddr = (unsigned long)area-\u003eaddr;\nmm/vmalloc.c:3657:\tif (vmap_pages_range(addr, addr + size, pgprot_nx(prot),\nmm/vmalloc.c-3658-\t\t\t\tpages, PAGE_SHIFT) \u003c 0) {\n"
} |
| 27/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 18312 output: 35 thoughts: 81 Thoughts: Here's my summary, as I delve into the code: **Analyzing `vmap()`'s Failure Scenarios** Okay, so I've noticed that `vmap()`, `vm_map_ram()`, and `vm_area_map_pages()` all leverage `vmap_pages_range()`. That's the common core. My real interest lies in what happens *when* `vmap_pages_range()` fails within the `vmap()` context. Where are the cleanup paths? What error handling is present? I'm zeroing in on lines 3650 through 3665 in `mm/vmalloc.c`. Let's see what the codepaths look like when it's unable to map those pages. |
| 28/2 | 2026/10/09 09:35 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 3650,
"LineCount": 20
}Results: {
"Contents": "3650:\t\n3651:\t\tsize = (unsigned long)count \u003c\u003c PAGE_SHIFT;\n3652:\t\tarea = get_vm_area_caller(size, flags, __builtin_return_address(0));\n3653:\t\tif (!area)\n3654:\t\t\treturn NULL;\n3655:\t\n3656:\t\taddr = (unsigned long)area-\u003eaddr;\n3657:\t\tif (vmap_pages_range(addr, addr + size, pgprot_nx(prot),\n3658:\t\t\t\t\tpages, PAGE_SHIFT) \u003c 0) {\n3659:\t\t\tvunmap(area-\u003eaddr);\n3660:\t\t\treturn NULL;\n3661:\t\t}\n3662:\t\n3663:\t\tif (flags \u0026 VM_MAP_PUT_PAGES) {\n3664:\t\t\tarea-\u003epages = pages;\n3665:\t\t\tarea-\u003enr_pages = count;\n3666:\t\t}\n3667:\t\treturn area-\u003eaddr;\n3668:\t}\n3669:\tEXPORT_SYMBOL(vmap);\n"
} |
| 29/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 18886 output: 23 thoughts: 726 Thoughts: **Analyzing the Changes to `__vmap_pages_range_noflush` and Related Functions** Okay, let's break this down. My initial observation is focused on the additions to `__vmap_pages_range_noflush`. Two `WARN_ON_ONCE` checks were introduced: one to ensure `addr` is less than `end`, and another to verify that `page_shift` isn't less than `PAGE_SHIFT`. These are basic sanity checks, likely added for robustness, preventing some undefined behavior or errors that could arise with invalid inputs. This suggests a desire to catch corner cases that might have been missed previously and to improve error handling in the vmap code. Now, let's trace how the error handling propagates. I see that `vmap_page_range` calls `__vunmap_range_noflush` if an error occurs. In the `__vmap_pages_range_noflush` function itself, if `err` is set, indicating a failure during PTE installation, it calls `__vunmap_range_noflush` to undo any partial mapping. `vmap_pages_range_noflush` also includes `kmsan_vunmap_range_noflush` on failure which is part of the KMSAN shadow mapping mechanism. I would surmise that `kmsan_vunmap_range_noflush` does what the name implies. This undoing of mappings upon failure is a standard defensive programming technique to ensure a consistent state. The key point seems to be in `pcpu_map_pages`. The patch altered the behavior of error handling in `pcpu_map_pages`. Before this patch, it would unmap pages for *all* target CPUs, including the CPU that experienced the error. Now, it only unmaps pages for CPUs *other* than the one that failed. The assumption is that the failing mapping on the failing CPU undoes itself, which seems logical to prevent double free. Lastly, I see how KMSAN's shadow mapping is affected. In `kmsan_vmap_pages_range_noflush`, if `mapped` is true (meaning a shadow mapping was set up), it calls `__vunmap_range_noflush` to undo that shadow mapping. The logic here is straightforward: clean up the shadow mapping on error. This has piqued my curiosity. I'd like to look at all the callers of `vmap_page_range` to see where else this error handling strategy comes into play, to get a better sense of the overall impact. |
| 30/2 | 2026/10/09 09:35 | tool | grepper |
0mArgs:{
"Expression": "\\bvmap_page_range\\b"
}Results: {
"Output": "arch/arm/mm/ioremap.c=111=int ioremap_page(unsigned long virt, unsigned long phys,\n--\narch/arm/mm/ioremap.c-113-{\narch/arm/mm/ioremap.c:114:\treturn vmap_page_range(virt, virt + PAGE_SIZE, phys,\narch/arm/mm/ioremap.c-115-\t\t\t __pgprot(mtype-\u003eprot_pte));\n--\narch/arm/mm/ioremap.c=484=int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)\n--\narch/arm/mm/ioremap.c-493-\narch/arm/mm/ioremap.c:494:\treturn vmap_page_range(vaddr, vaddr + resource_size(res), phys_addr,\narch/arm/mm/ioremap.c-495-\t\t\t __pgprot(get_mem_type(pci_ioremap_mem_type)-\u003eprot_pte));\n--\narch/loongarch/kernel/acpi.c=70=void acpi_add_early_pio(void)\n--\narch/loongarch/kernel/acpi.c-73-\t\tacpi_pio = true;\narch/loongarch/kernel/acpi.c:74:\t\tvmap_page_range(PIO_BASE, PIO_BASE + PIO_SIZE,\narch/loongarch/kernel/acpi.c-75-\t\t\t\tLOONGSON_LIO_BASE, pgprot_device(PAGE_KERNEL));\n--\narch/loongarch/kernel/setup.c=466=static int __init add_legacy_isa_io(struct fwnode_handle *fwnode,\n--\narch/loongarch/kernel/setup.c-495-\tvaddr = (unsigned long)(PCI_IOBASE + range-\u003eio_start);\narch/loongarch/kernel/setup.c:496:\tvmap_page_range(vaddr, vaddr + size, hw_start, pgprot_device(PAGE_KERNEL));\narch/loongarch/kernel/setup.c-497-\n--\narch/mips/loongson64/init.c=153=static int __init add_legacy_isa_io(struct fwnode_handle *fwnode, resource_size_t hw_start,\n--\narch/mips/loongson64/init.c-183-\narch/mips/loongson64/init.c:184:\tvmap_page_range(vaddr, vaddr + size, hw_start, pgprot_device(PAGE_KERNEL));\narch/mips/loongson64/init.c-185-\n--\narch/powerpc/kernel/isa-bridge.c=42=static void remap_isa_base(phys_addr_t pa, unsigned long size)\n--\narch/powerpc/kernel/isa-bridge.c-48-\tif (slab_is_available()) {\narch/powerpc/kernel/isa-bridge.c:49:\t\tvmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,\narch/powerpc/kernel/isa-bridge.c-50-\t\t\t\tpgprot_noncached(PAGE_KERNEL));\n--\ndrivers/pci/pci.c=4112=int pci_remap_iospace(const struct resource *res, phys_addr_t phys_addr)\n--\ndrivers/pci/pci.c-4122-\ndrivers/pci/pci.c:4123:\treturn vmap_page_range(vaddr, vaddr + resource_size(res), phys_addr,\ndrivers/pci/pci.c-4124-\t\t\t pgprot_device(PAGE_KERNEL));\n--\ninclude/linux/io.h=28=int ioremap_page_range(unsigned long addr, unsigned long end,\ninclude/linux/io.h-29-\t\t phys_addr_t phys_addr, pgprot_t prot);\ninclude/linux/io.h:30:int vmap_page_range(unsigned long addr, unsigned long end,\ninclude/linux/io.h-31-\t\t phys_addr_t phys_addr, pgprot_t prot);\n--\ninclude/linux/io.h=33=static inline int ioremap_page_range(unsigned long addr, unsigned long end,\n--\ninclude/linux/io.h-37-}\ninclude/linux/io.h:38:static inline int vmap_page_range(unsigned long addr, unsigned long end,\ninclude/linux/io.h-39-\t\t\t\t phys_addr_t phys_addr, pgprot_t prot)\n--\nkernel/trace/trace.c-52-#include \u003clinux/sort.h\u003e\nkernel/trace/trace.c:53:#include \u003clinux/io.h\u003e /* vmap_page_range() */\nkernel/trace/trace.c-54-#include \u003clinux/fs_context.h\u003e\n--\nkernel/trace/trace.c=8786=static u64 map_pages(unsigned long start, unsigned long size)\n--\nkernel/trace/trace.c-8798-\nkernel/trace/trace.c:8799:\tret = vmap_page_range(vmap_start, vmap_end,\nkernel/trace/trace.c-8800-\t\t\t start, pgprot_nx(PAGE_KERNEL));\n--\nmm/vmalloc.c=321=static int vmap_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-354-\nmm/vmalloc.c:355:int vmap_page_range(unsigned long addr, unsigned long end,\nmm/vmalloc.c-356-\t\t phys_addr_t phys_addr, pgprot_t prot)\n--\nmm/vmalloc.c=372=int ioremap_page_range(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-388-\t}\nmm/vmalloc.c:389:\treturn vmap_page_range(addr, end, phys_addr, prot);\nmm/vmalloc.c-390-}\n"
} |
| 31/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 21734 output: 24 thoughts: 1847 Thoughts: **Fuzzing Analysis: `__vmap_pages_range_noflush` and FocusSymbol Determination** Okay, so I'm looking at this patch and it's clear the core change is the introduction of new assertions, `WARN_ON_ONCE`, within `__vmap_pages_range_noflush`. That function is *definitely* reachable; the code shows it's used across several architectures, including amd64 in common virtualization setups like QEMU/KVM. Specifically, I see its part of the path: `__vmalloc_node_range()` -> `__vmalloc_area_node()` -> `__vmap_pages_range()` -> `vmap_pages_range_noflush()` -> `__vmap_pages_range_noflush()`, which goes through core memory management code in `mm/vmalloc.c`. This triggers the "WorthFuzzing = true" flag. Now, the question is how to use fuzzing effectively. The document says to extract "FocusSymbols" to avoid diluting the fuzzer. I *must* avoid listing generic, ubiquitous functions like general memory allocators or deallocators. The key here is to target specific entrypoints or *where* the logic is *actually* modified. So, what are the modified functions in this patch? I've got a list from the text: * `vmap_page_range` (in `mm/vmalloc.c`) * `__vmap_pages_range_noflush` (in `mm/vmalloc.c`) * `vmap_pages_range_noflush` (in `mm/vmalloc.c`) * `kmsan_vmap_pages_range_noflush` (in `mm/kmsan/shadow.c`) * `pcpu_map_pages` (in `mm/percpu-vm.c`) * `remap_isa_base` (in `arch/powerpc/kernel/isa-bridge.c`) * `ioremap_phb` (in `arch/powerpc/kernel/pci_64.c`) The crucial question is about `__vmap_pages_range_noflush`. Is it ubiquitous? *That's* the function the patch is actually modifying. It's *not* a generic allocator, right? It's involved in virtual memory mapping, which, while important, is *not* the same as `kmalloc`. It's used for allocating large buffers, bpf programs, module loading, large ioctl buffers, sound buffers, etc. The note says specifically to avoid "general memory allocators and deallocators". Importantly, it's *not* static, it's an exported C function in `mm/vmalloc.c`. Same for `vmap_page_range` and `vmap_pages_range_noflush` and `kmsan_vmap_pages_range_noflush`. However, `pcpu_map_pages` *is* static. This means that *because* `__vmap_pages_range_noflush` is a distinct global symbol where the patch makes code modifications, it *is* an *ideal* FocusSymbol. This patch introduces a key runtime check in `__vmap_pages_range_noflush` that should be targeted by the fuzzer. |
| 32/2 | 2026/10/09 09:35 | tool | grepper |
0mArgs:{
"Expression": "\\bpcpu_map_pages\\b"
}Results: {
"Output": "mm/percpu-vm.c=62=static void pcpu_free_pages(struct pcpu_chunk *chunk,\n--\nmm/percpu-vm.c-87- * The allocation is for @chunk. Percpu core doesn't care about the\nmm/percpu-vm.c:88: * content of @pages and will pass it verbatim to pcpu_map_pages().\nmm/percpu-vm.c-89- */\n--\nmm/percpu-vm.c=201=static int __pcpu_map_pages(unsigned long addr, struct page **pages,\n--\nmm/percpu-vm.c-220-/**\nmm/percpu-vm.c:221: * pcpu_map_pages - map pages into a pcpu_chunk\nmm/percpu-vm.c-222- * @chunk: chunk of interest\n--\nmm/percpu-vm.c-234- */\nmm/percpu-vm.c:235:static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,\nmm/percpu-vm.c-236-\t\t\t int page_start, int page_end, gfp_t gfp)\n--\nmm/percpu-vm.c=298=static int pcpu_populate_chunk(struct pcpu_chunk *chunk,\n--\nmm/percpu-vm.c-309-\nmm/percpu-vm.c:310:\tif (pcpu_map_pages(chunk, pages, page_start, page_end, gfp)) {\nmm/percpu-vm.c-311-\t\tpcpu_free_pages(chunk, pages, page_start, page_end);\n"
} |
| 33/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 24779 output: 20 thoughts: 14 Thoughts: Here's my summary, as though I'm thinking through this process: **Investigating the Caller of `pcpu_populate_chunk`** Okay, so I need to figure out exactly *who* is calling `pcpu_populate_chunk`. This function is core to how the system handles per-CPU data structures, so understanding its usage is critical for optimization, debugging, or even just understanding system behavior. I can't just dive in without knowing the calling context. Let's trace back from the function itself. I need to identify *all* the places where `pcpu_populate_chunk` is being invoked. Armed with that information, I can better understand the intent behind the call, what data is being passed, and what's dependent on the call. This is going to involve some careful code inspection, perhaps using a debugger, grep, or a static analysis tool, depending on the size and complexity of the codebase. |
| 34/2 | 2026/10/09 09:35 | tool | grepper |
0mArgs:{
"Expression": "pcpu_populate_chunk"
}Results: {
"Output": "mm/percpu-km.c=35=static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,\n--\nmm/percpu-km.c-40-\nmm/percpu-km.c:41:static int pcpu_populate_chunk(struct pcpu_chunk *chunk,\nmm/percpu-km.c-42-\t\t\t int page_start, int page_end, gfp_t gfp)\n--\nmm/percpu-vm.c=277=static void pcpu_post_map_flush(struct pcpu_chunk *chunk,\n--\nmm/percpu-vm.c-285-/**\nmm/percpu-vm.c:286: * pcpu_populate_chunk - populate and map an area of a pcpu_chunk\nmm/percpu-vm.c-287- * @chunk: chunk of interest\n--\nmm/percpu-vm.c-297- */\nmm/percpu-vm.c:298:static int pcpu_populate_chunk(struct pcpu_chunk *chunk,\nmm/percpu-vm.c-299-\t\t\t int page_start, int page_end, gfp_t gfp)\n--\nmm/percpu.c=1535=static void pcpu_chunk_depopulated(struct pcpu_chunk *chunk,\n--\nmm/percpu.c-1556- *\nmm/percpu.c:1557: * pcpu_populate_chunk\t\t- populate the specified range of a chunk\nmm/percpu.c-1558- * pcpu_depopulate_chunk\t- depopulate the specified range of a chunk\n--\nmm/percpu.c-1564- */\nmm/percpu.c:1565:static int pcpu_populate_chunk(struct pcpu_chunk *chunk,\nmm/percpu.c-1566-\t\t\t int page_start, int page_end, gfp_t gfp);\n--\nmm/percpu.c=1733=void __percpu *pcpu_alloc_noprof(size_t size, size_t align, bool reserved,\n--\nmm/percpu.c-1881-\nmm/percpu.c:1882:\t\t\tret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);\nmm/percpu.c-1883-\n--\nmm/percpu.c=2011=static void pcpu_balance_populated(void)\n--\nmm/percpu.c-2060-\t\t\tspin_unlock_irq(\u0026pcpu_lock);\nmm/percpu.c:2061:\t\t\tret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);\nmm/percpu.c-2062-\t\t\tcond_resched();\n"
} |
| 35/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 25724 output: 36 thoughts: 57 Thoughts: Okay, let's dive into this kernel configuration puzzle. **Pinpointing the Right Configuration Knobs** My immediate concern is figuring out the precise `CONFIG` options that control the behavior of those crucial memory management files: `mm/percpu-vm.c`, `mm/kmsan/shadow.c`, and `mm/vmalloc.c`. Understanding these options is paramount to understanding how these files operate, and how I can control their behavior. The first logical step is to check the `mm/Makefile`. That should give me the initial clues I need to start my investigation. This will also give me a basis to expand my research. |
| 36/2 | 2026/10/09 09:35 | tool | grepper |
0mArgs:{
"Expression": "(vmalloc|percpu-vm|shadow)\\.o",
"PathPrefixes": [
"mm/"
]
}Results: {
"Output": "mm/Makefile=37=mmu-$(CONFIG_MMU)\t:= highmem.o memory.o mincore.o \\\n--\nmm/Makefile-39-\t\t\t msync.o page_vma_mapped.o pagewalk.o \\\nmm/Makefile:40:\t\t\t pgtable-generic.o rmap.o vmalloc.o vma.o vma_exec.o\nmm/Makefile-41-\n--\nmm/kasan/Makefile=14=CFLAGS_REMOVE_report_sw_tags.o = $(CC_FLAGS_FTRACE)\nmm/kasan/Makefile:15:CFLAGS_REMOVE_shadow.o = $(CC_FLAGS_FTRACE)\nmm/kasan/Makefile-16-CFLAGS_REMOVE_hw_tags.o = $(CC_FLAGS_FTRACE)\n--\nmm/kasan/Makefile=33=CFLAGS_report_sw_tags.o := $(CC_FLAGS_KASAN_RUNTIME)\nmm/kasan/Makefile:34:CFLAGS_shadow.o := $(CC_FLAGS_KASAN_RUNTIME)\nmm/kasan/Makefile-35-CFLAGS_hw_tags.o := $(CC_FLAGS_KASAN_RUNTIME)\n--\nmm/kasan/Makefile=51=obj-y := common.o report.o\nmm/kasan/Makefile:52:obj-$(CONFIG_KASAN_GENERIC) += init.o generic.o report_generic.o shadow.o quarantine.o\nmm/kasan/Makefile-53-obj-$(CONFIG_KASAN_HW_TAGS) += hw_tags.o report_hw_tags.o tags.o report_tags.o\nmm/kasan/Makefile:54:obj-$(CONFIG_KASAN_SW_TAGS) += init.o report_sw_tags.o shadow.o sw_tags.o tags.o report_tags.o\nmm/kasan/Makefile-55-\n--\nmm/kmsan/Makefile-5-#\nmm/kmsan/Makefile:6:obj-y := core.o instrumentation.o init.o hooks.o report.o shadow.o\nmm/kmsan/Makefile-7-\n--\nmm/kmsan/Makefile=22=CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE)\nmm/kmsan/Makefile:23:CFLAGS_REMOVE_shadow.o = $(CC_FLAGS_FTRACE)\nmm/kmsan/Makefile-24-\n--\nmm/kmsan/Makefile=29=CFLAGS_report.o := $(CC_FLAGS_KMSAN_RUNTIME)\nmm/kmsan/Makefile:30:CFLAGS_shadow.o := $(CC_FLAGS_KMSAN_RUNTIME)\nmm/kmsan/Makefile-31-\n"
} |
| 37/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 26610 output: 27 thoughts: 26 Thoughts: Here's a summary of my thought process: **Diving into Build Dependencies: `mm/percpu-vm.c` and `mm/kmsan/`** Okay, so I'm thinking I need to understand how these specific files, `mm/percpu-vm.c` and the `mm/kmsan/` directory, are built within the kernel build system. I'm going to start by looking at the build rules and dependencies associated with them. This likely means tracking down the relevant Kconfig options and Makefiles to see what triggers their inclusion and how they're compiled. Specifically, I'm probably looking for: * **Kconfig settings:** I want to see if there are specific configuration options that enable or disable the compilation of these parts of the kernel. Are they tied to specific architectures, features, or build flags? * **Makefile dependencies:** I need to find the Makefiles that handle these files. What other source files, libraries, or build targets are they dependent on? How are compilation flags handled (e.g., `-D`, `-I`, etc.)? * **Module or Built-in:** Are they built as loadable modules or are they compiled directly into the kernel image? * **Build variables:** I'm interested in any build-time variables that could influence the compilation or behavior of these components. Basically, I need a clear picture of how the build system integrates these pieces and what factors control their presence and behavior in the final kernel. This is essential for understanding how the kernel works and how to manage the build process. |
| 38/2 | 2026/10/09 09:35 | tool | grepper |
0mArgs:{
"Expression": "percpu-vm",
"PathPrefixes": [
"mm/"
]
}Results: {
"Output": "mm/percpu-vm.c-2-/*\nmm/percpu-vm.c:3: * mm/percpu-vm.c - vmalloc area based chunk allocation\nmm/percpu-vm.c-4- *\n--\nmm/percpu.c=1574=static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);\n--\nmm/percpu.c-1578-#else\nmm/percpu.c:1579:#include \"percpu-vm.c\"\nmm/percpu.c-1580-#endif\n"
} |
| 39/2 | 2026/10/09 09:35 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 27156 output: 35 thoughts: 31 Thoughts: Okay, here's my interpretation of what's going on, thinking through this code: **Diving into `mm/percpu.c` - Lines Around 1575** Alright, let's get into the nitty-gritty. I'm taking a look at the `mm/percpu.c` file, specifically around line 1575. My initial goal is to understand the context surrounding this particular code section. I need to refresh my memory on what per-CPU memory management entails and how the kernel handles it at this level. I'll be reading the surrounding code for a holistic understanding. I'm focusing on the implementation details, potentially looking for data structures, allocation/deallocation strategies, or synchronization primitives related to per-CPU memory. This is probably related to how the kernel manages memory on a per-CPU basis for efficiency, avoiding contention, and improving performance. I'm expecting to find details on how data is allocated, accessed, and freed for each CPU independently. Now, let's see what the code actually reveals. |
| 40/2 | 2026/10/09 09:36 | tool | read-file |
0mArgs:{
"File": "mm/percpu.c",
"FirstLine": 1570,
"LineCount": 20
}Results: {
"Contents": "1570:\t\t\t\t\t int page_start, int page_end);\n1571:\tstatic struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp);\n1572:\tstatic void pcpu_destroy_chunk(struct pcpu_chunk *chunk);\n1573:\tstatic struct page *pcpu_addr_to_page(void *addr);\n1574:\tstatic int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);\n1575:\t\n1576:\t#ifdef CONFIG_NEED_PER_CPU_KM\n1577:\t#include \"percpu-km.c\"\n1578:\t#else\n1579:\t#include \"percpu-vm.c\"\n1580:\t#endif\n1581:\t\n1582:\t/**\n1583:\t * pcpu_chunk_addr_search - determine chunk containing specified address\n1584:\t * @addr: address for which the chunk needs to be determined.\n1585:\t *\n1586:\t * This is an internal function that handles all but static allocations.\n1587:\t * Static percpu address values should never be passed into the allocator.\n1588:\t *\n1589:\t * RETURNS:\n"
} |
| 41/2 | 2026/10/09 09:36 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 27788 output: 25 thoughts: 109 Thoughts: **My Analysis of Per-CPU Virtual Memory and Kernel Memory Sanitization** Okay, so here's what I'm piecing together about the kernel's memory management. It looks like `percpu-vm.c` is brought into the picture through `mm/percpu.c`, specifically when the `CONFIG_NEED_PER_CPU_KM` option *isn't* enabled. This is standard on systems with Memory Management Units (MMUs), like most modern amd64 architectures, so that's the common case I need to focus on. Then, there's `mm/Makefile`. That file tells me that `vmalloc.o` gets built when `CONFIG_MMU` is active – which, again, is the typical setting on amd64 systems. So, the vmalloc allocator is essential. My next step has to be examining the build process for `mm/kmsan/`. I have to dig further. I need to figure out under what conditions the kernel memory sanitizer code is compiled. The makefile in `mm/` is the next place to look. |
| 42/2 | 2026/10/09 09:36 | tool | grepper |
0mArgs:{
"Expression": "kmsan",
"PathPrefixes": [
"mm/"
]
}Results: {
"Output": "\nFull output is too long, showing 200 out of 1337 lines.\nUse more precise expression or PathPrefixes if possible.\n\nNumber of matching lines per file (19 files in total):\nmm/Makefile:1\nmm/kfence/core.c:1\nmm/kmsan/Makefile:3\nmm/kmsan/core.c:52\nmm/kmsan/hooks.c:104\nmm/kmsan/init.c:17\nmm/kmsan/instrumentation.c:40\nmm/kmsan/kmsan.h:45\nmm/kmsan/kmsan_test.c:41\nmm/kmsan/report.c:25\nmm/kmsan/shadow.c:43\nmm/maccess.c:2\nmm/memory.c:2\nmm/mm_init.c:3\nmm/page_alloc.c:5\nmm/slab.h:3\nmm/slub.c:10\nmm/vmalloc.c:4\nmm/zsmalloc.c:1\n\nmm/Makefile=94=obj-$(CONFIG_KFENCE) += kfence/\nmm/Makefile:95:obj-$(CONFIG_KMSAN)\t+= kmsan/\nmm/Makefile-96-obj-$(CONFIG_FAILSLAB) += failslab.o\n--\nmm/kfence/core.c=297=metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state next,\n--\nmm/kfence/core.c-334-#ifdef CONFIG_KMSAN\nmm/kfence/core.c:335:#define check_canary_attributes noinline __no_kmsan_checks\nmm/kfence/core.c-336-#else\n--\nmm/kmsan/Makefile=30=CFLAGS_shadow.o := $(CC_FLAGS_KMSAN_RUNTIME)\nmm/kmsan/Makefile-31-\nmm/kmsan/Makefile:32:obj-$(CONFIG_KMSAN_KUNIT_TEST) += kmsan_test.o\nmm/kmsan/Makefile:33:KMSAN_SANITIZE_kmsan_test.o := y\nmm/kmsan/Makefile:34:CFLAGS_kmsan_test.o += $(call cc-disable-warning, uninitialized)\n--\nmm/kmsan/core.c-15-#include \u003clinux/kernel.h\u003e\nmm/kmsan/core.c:16:#include \u003clinux/kmsan_types.h\u003e\nmm/kmsan/core.c-17-#include \u003clinux/memory.h\u003e\n--\nmm/kmsan/core.c-30-#include \"../vmalloc.h\"\nmm/kmsan/core.c:31:#include \"kmsan.h\"\nmm/kmsan/core.c-32-\nmm/kmsan/core.c:33:bool kmsan_enabled __read_mostly;\nmm/kmsan/core.c-34-\nmm/kmsan/core.c-35-/*\nmm/kmsan/core.c:36: * Per-CPU KMSAN context to be used in interrupts, where current-\u003ekmsan is\nmm/kmsan/core.c-37- * unavailable.\nmm/kmsan/core.c-38- */\nmm/kmsan/core.c:39:DEFINE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);\nmm/kmsan/core.c-40-\nmm/kmsan/core.c:41:void kmsan_internal_task_create(struct task_struct *task)\nmm/kmsan/core.c-42-{\nmm/kmsan/core.c:43:\tstruct kmsan_ctx *ctx = \u0026task-\u003ekmsan_ctx;\nmm/kmsan/core.c-44-\tstruct thread_info *info = current_thread_info();\n--\nmm/kmsan/core.c-46-\t__memset(ctx, 0, sizeof(*ctx));\nmm/kmsan/core.c:47:\tkmsan_internal_unpoison_memory(info, sizeof(*info), false);\nmm/kmsan/core.c-48-}\nmm/kmsan/core.c-49-\nmm/kmsan/core.c:50:void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,\nmm/kmsan/core.c-51-\t\t\t\t unsigned int poison_flags)\n--\nmm/kmsan/core.c-53-\tu32 extra_bits =\nmm/kmsan/core.c:54:\t\tkmsan_extra_bits(/*depth*/ 0, poison_flags \u0026 KMSAN_POISON_FREE);\nmm/kmsan/core.c-55-\tbool checked = poison_flags \u0026 KMSAN_POISON_CHECK;\n--\nmm/kmsan/core.c-57-\nmm/kmsan/core.c:58:\thandle = kmsan_save_stack_with_flags(flags, extra_bits);\nmm/kmsan/core.c:59:\tkmsan_internal_set_shadow_origin(address, size, -1, handle, checked);\nmm/kmsan/core.c-60-}\nmm/kmsan/core.c-61-\nmm/kmsan/core.c:62:void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked)\nmm/kmsan/core.c-63-{\nmm/kmsan/core.c:64:\tkmsan_internal_set_shadow_origin(address, size, 0, 0, checked);\nmm/kmsan/core.c-65-}\nmm/kmsan/core.c-66-\nmm/kmsan/core.c:67:depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,\nmm/kmsan/core.c-68-\t\t\t\t\t\t unsigned int extra)\n--\nmm/kmsan/core.c-80-/* Copy the metadata following the memmove() behavior. */\nmm/kmsan/core.c:81:void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n)\nmm/kmsan/core.c-82-{\n--\nmm/kmsan/core.c-90-\nmm/kmsan/core.c:91:\tshadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW);\nmm/kmsan/core.c-92-\tif (!shadow_dst)\nmm/kmsan/core.c-93-\t\treturn;\nmm/kmsan/core.c:94:\tKMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n));\nmm/kmsan/core.c-95-\talign_shadow_dst =\n--\nmm/kmsan/core.c-97-\nmm/kmsan/core.c:98:\tshadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW);\nmm/kmsan/core.c-99-\tif (!shadow_src) {\nmm/kmsan/core.c-100-\t\t/* @src is untracked: mark @dst as initialized. */\nmm/kmsan/core.c:101:\t\tkmsan_internal_unpoison_memory(dst, n, /*checked*/ false);\nmm/kmsan/core.c-102-\t\treturn;\nmm/kmsan/core.c-103-\t}\nmm/kmsan/core.c:104:\tKMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n));\nmm/kmsan/core.c-105-\nmm/kmsan/core.c:106:\torigin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN);\nmm/kmsan/core.c:107:\torigin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN);\nmm/kmsan/core.c-108-\tKMSAN_WARN_ON(!origin_dst || !origin_src);\n--\nmm/kmsan/core.c-131-\t\t\t/*\nmm/kmsan/core.c:132:\t\t\t * kmsan_internal_chain_origin() may return\nmm/kmsan/core.c-133-\t\t\t * NULL, but we don't want to lose the previous\n--\nmm/kmsan/core.c-135-\t\t\t */\nmm/kmsan/core.c:136:\t\t\tnew_origin = kmsan_internal_chain_origin(old_origin);\nmm/kmsan/core.c-137-\t\t\tif (!new_origin)\n--\nmm/kmsan/core.c-145-\nmm/kmsan/core.c:146:depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id)\nmm/kmsan/core.c-147-{\n--\nmm/kmsan/core.c-163-\textra_bits = stack_depot_get_extra_bits(id);\nmm/kmsan/core.c:164:\tdepth = kmsan_depth_from_eb(extra_bits);\nmm/kmsan/core.c:165:\tuaf = kmsan_uaf_from_eb(extra_bits);\nmm/kmsan/core.c-166-\n--\nmm/kmsan/core.c-176-\tdepth++;\nmm/kmsan/core.c:177:\textra_bits = kmsan_extra_bits(depth, uaf);\nmm/kmsan/core.c-178-\nmm/kmsan/core.c-179-\tentries[0] = KMSAN_CHAIN_MAGIC_ORIGIN;\nmm/kmsan/core.c:180:\tentries[1] = kmsan_save_stack_with_flags(__GFP_HIGH, 0);\nmm/kmsan/core.c-181-\tentries[2] = id;\n--\nmm/kmsan/core.c-186-\t */\nmm/kmsan/core.c:187:\tkmsan_internal_unpoison_memory(entries, sizeof(entries), false);\nmm/kmsan/core.c-188-\thandle = stack_depot_save(entries, ARRAY_SIZE(entries), __GFP_HIGH);\n--\nmm/kmsan/core.c-191-\nmm/kmsan/core.c:192:void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b,\nmm/kmsan/core.c-193-\t\t\t\t u32 origin, bool checked)\n--\nmm/kmsan/core.c-199-\nmm/kmsan/core.c:200:\tKMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size));\nmm/kmsan/core.c:201:\tshadow_start = kmsan_get_metadata(addr, KMSAN_META_SHADOW);\nmm/kmsan/core.c-202-\tif (!shadow_start) {\nmm/kmsan/core.c-203-\t\t/*\nmm/kmsan/core.c:204:\t\t * kmsan_metadata_is_contiguous() is true, so either all shadow\nmm/kmsan/core.c-205-\t\t * and origin pages are NULL, or all are non-NULL.\n--\nmm/kmsan/core.c-225-\torigin_start =\nmm/kmsan/core.c:226:\t\t(u32 *)kmsan_get_metadata((void *)address, KMSAN_META_ORIGIN);\nmm/kmsan/core.c-227-\n--\nmm/kmsan/core.c-239-\nmm/kmsan/core.c:240:struct page *kmsan_vmalloc_to_page_or_null(void *vaddr)\nmm/kmsan/core.c-241-{\n--\nmm/kmsan/core.c-250-\nmm/kmsan/core.c:251:void kmsan_internal_check_memory(void *addr, size_t size,\nmm/kmsan/core.c-252-\t\t\t\t const void __user *user_addr, int reason)\n--\nmm/kmsan/core.c-263-\t\treturn;\nmm/kmsan/core.c:264:\tKMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size));\nmm/kmsan/core.c-265-\twhile (pos \u003c size) {\n--\nmm/kmsan/core.c-267-\t\t\t\t PAGE_SIZE - ((addr64 + pos) % PAGE_SIZE));\nmm/kmsan/core.c:268:\t\tshadow = kmsan_get_metadata((void *)(addr64 + pos),\nmm/kmsan/core.c-269-\t\t\t\t\t KMSAN_META_SHADOW);\n--\nmm/kmsan/core.c-275-\t\t\tif (cur_origin) {\nmm/kmsan/core.c:276:\t\t\t\tkmsan_report(cur_origin, addr, size,\nmm/kmsan/core.c-277-\t\t\t\t\t cur_off_start, pos - 1, user_addr,\n--\nmm/kmsan/core.c-291-\t\t\t\tif (cur_origin) {\nmm/kmsan/core.c:292:\t\t\t\t\tkmsan_report(cur_origin, addr, size,\nmm/kmsan/core.c-293-\t\t\t\t\t\t cur_off_start, pos + i - 1,\n--\nmm/kmsan/core.c-299-\t\t\t}\nmm/kmsan/core.c:300:\t\t\torigin = kmsan_get_metadata((void *)(addr64 + pos + i),\nmm/kmsan/core.c-301-\t\t\t\t\t\t KMSAN_META_ORIGIN);\n--\nmm/kmsan/core.c-309-\t\t\t\tif (cur_origin) {\nmm/kmsan/core.c:310:\t\t\t\t\tkmsan_report(cur_origin, addr, size,\nmm/kmsan/core.c-311-\t\t\t\t\t\t cur_off_start, pos + i - 1,\n--\nmm/kmsan/core.c-321-\tif (cur_origin) {\nmm/kmsan/core.c:322:\t\tkmsan_report(cur_origin, addr, size, cur_off_start, pos - 1,\nmm/kmsan/core.c-323-\t\t\t user_addr, reason);\n--\nmm/kmsan/core.c-326-\nmm/kmsan/core.c:327:bool kmsan_metadata_is_contiguous(void *addr, size_t size)\nmm/kmsan/core.c-328-{\n--\nmm/kmsan/core.c-342-\nmm/kmsan/core.c:343:\tcur_shadow = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ false);\nmm/kmsan/core.c-344-\tif (!cur_shadow)\nmm/kmsan/core.c-345-\t\tall_untracked = true;\nmm/kmsan/core.c:346:\tcur_origin = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ true);\nmm/kmsan/core.c-347-\tif (all_untracked \u0026\u0026 cur_origin)\n--\nmm/kmsan/core.c-352-\t cur_origin = next_origin, next_addr += PAGE_SIZE) {\nmm/kmsan/core.c:353:\t\tnext_shadow = kmsan_get_metadata((void *)next_addr, false);\nmm/kmsan/core.c:354:\t\tnext_origin = kmsan_get_metadata((void *)next_addr, true);\nmm/kmsan/core.c-355-\t\tif (all_untracked) {\n--\nmm/kmsan/core.c-376-\t next_origin);\nmm/kmsan/core.c:377:\torigin_p = kmsan_get_metadata(addr, KMSAN_META_ORIGIN);\nmm/kmsan/core.c-378-\tif (origin_p) {\nmm/kmsan/core.c-379-\t\tpr_err(\"Origin: %08x\\n\", *origin_p);\nmm/kmsan/core.c:380:\t\tkmsan_print_origin(*origin_p);\nmm/kmsan/core.c-381-\t} else {\n--\nmm/kmsan/hooks.c-14-#include \u003clinux/gfp.h\u003e\nmm/kmsan/hooks.c:15:#include \u003clinux/kmsan.h\u003e\nmm/kmsan/hooks.c-16-#include \u003clinux/mm.h\u003e\n--\nmm/kmsan/hooks.c-27-#include \"../slab.h\"\nmm/kmsan/hooks.c:28:#include \"kmsan.h\"\nmm/kmsan/hooks.c-29-\n--\nmm/kmsan/hooks.c-31- * Instrumented functions shouldn't be called under\nmm/kmsan/hooks.c:32: * kmsan_enter_runtime()/kmsan_leave_runtime(), because this will lead to\nmm/kmsan/hooks.c-33- * skipping effects of functions like memset() inside instrumented code.\n--\nmm/kmsan/hooks.c-35-\n\n"
} |
| 43/2 | 2026/10/09 09:36 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 32499 output: 19 thoughts: 398 Thoughts: **Analyzing KMSAN and its Relationship to Memory Management** Okay, let's break this down. First, `CONFIG_MMU` is a given – that's standard. The question then becomes: Does KMSAN require us to reach `mm/kmsan/shadow.c`? The answer is yes; `CONFIG_KMSAN` is what triggers the compilation of `mm/kmsan/shadow.c`. But what about `mm/vmalloc.c` and `mm/percpu-vm.c`? Those are compiled as long as `CONFIG_MMU` is enabled, which is the case for most architectures, certainly on amd64. Now, does KMSAN have to be enabled to get to `__vmap_pages_range_noflush`? No, since that's in `mm/vmalloc.c` and depends on `CONFIG_MMU`. That's always compiled. But hold on, can `kmsan_vmap_pages_range_noflush` get compiled without KMSAN? Checking `include/linux/kmsan.h` clarifies that when `CONFIG_KMSAN` is not set, `kmsan_vmap_pages_range_noflush` becomes an inline function that returns 0. So, it *can* be compiled without KMSAN. And when `CONFIG_KMSAN=y`, then `mm/kmsan/shadow.c` is definitely compiled. So, what Kconfig options are crucial for `EnableConfigs`? Well, `CONFIG_MMU` is always there on amd64 by default. But `CONFIG_KMSAN`? Perhaps we want to list that one. If KMSAN is enabled, then `mm/kmsan/shadow.c` *is* reachable. The next step is to understand what KMSAN actually depends on; so I'll check `init/Kconfig` or `mm/kasan/Kconfig` (or wherever KMSAN's defined) to nail down its dependencies. |
| 44/2 | 2026/10/09 09:36 | tool | grepper |
0mArgs:{
"Expression": "config KMSAN\\b"
}Results: {
"Output": "lib/Kconfig.kmsan=5=config HAVE_KMSAN_COMPILER\n--\nlib/Kconfig.kmsan-7-\nlib/Kconfig.kmsan:8:config KMSAN\nlib/Kconfig.kmsan-9-\tbool \"KMSAN: detector of uninitialized values use\"\n"
} |
| 45/2 | 2026/10/09 09:36 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 33430 output: 33 thoughts: 13 Thoughts: Here's my take on the thought process, tailored for an expert audience: **Diving into the KMSAN Kconfig** Alright, let's get down to brass tacks. I'm going to start by examining `lib/Kconfig.kmsan`. I'm immediately interested in seeing how kernel memory safety analysis (KMSAN) is configured and integrated within the build system. What are the key dependencies? Which Kconfig options are involved? I need to understand the granularity of control we have over KMSAN's behavior at build time. Is it a monolithic option, or are there more fine-grained controls for specific features or instrumentation levels? I’m particularly keen on seeing if there are any options related to performance overhead; I'm always looking for ways to balance the benefits of instrumentation with minimizing runtime impact. I want to see how KMSAN plays with other sanitizers, like KASAN; are they mutually exclusive, or can they be combined in any way? This is crucial for avoiding conflicts and ensuring we’re not unknowingly disabling one tool by enabling another. Also, I'll be keeping an eye out for any specific target architectures or kernel versions that are explicitly supported or excluded. I'm hoping to get a clear picture of the scope of KMSAN's applicability and how it's handled at the build level. Let's see what gems are hidden in this file. |
| 46/2 | 2026/10/09 09:36 | tool | read-file |
0mArgs:{
"File": "lib/Kconfig.kmsan",
"FirstLine": 1,
"LineCount": 40
}Results: {
"Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\tconfig HAVE_ARCH_KMSAN\n 3:\t\tbool\n 4:\t\n 5:\tconfig HAVE_KMSAN_COMPILER\n 6:\t\tdef_bool $(cc-option,-fsanitize=kernel-memory)\n 7:\t\n 8:\tconfig KMSAN\n 9:\t\tbool \"KMSAN: detector of uninitialized values use\"\n 10:\t\tdepends on HAVE_ARCH_KMSAN \u0026\u0026 HAVE_KMSAN_COMPILER\n 11:\t\tdepends on DEBUG_KERNEL \u0026\u0026 !KASAN \u0026\u0026 !KCSAN\n 12:\t\tdepends on !PREEMPT_RT\n 13:\t\tselect STACKDEPOT\n 14:\t\tselect STACKDEPOT_ALWAYS_INIT\n 15:\t\thelp\n 16:\t\t KernelMemorySanitizer (KMSAN) is a dynamic detector of uses of\n 17:\t\t uninitialized values in the kernel. It is based on compiler\n 18:\t\t instrumentation provided by Clang and thus requires Clang to build.\n 19:\t\n 20:\t\t An important note is that KMSAN is not intended for production use,\n 21:\t\t because it drastically increases kernel memory footprint and slows\n 22:\t\t the whole system down.\n 23:\t\n 24:\t\t See \u003cfile:Documentation/dev-tools/kmsan.rst\u003e for more details.\n 25:\t\n 26:\tif KMSAN\n 27:\t\n 28:\tconfig KMSAN_CHECK_PARAM_RETVAL\n 29:\t\tbool \"Check for uninitialized values passed to and returned from functions\"\n 30:\t\tdefault y\n 31:\t\thelp\n 32:\t\t If the compiler supports -fsanitize-memory-param-retval, KMSAN will\n 33:\t\t eagerly check every function parameter passed by value and every\n 34:\t\t function return value.\n 35:\t\n 36:\t\t Disabling KMSAN_CHECK_PARAM_RETVAL will result in tracking shadow for\n 37:\t\t function parameters and return values across function borders. This\n 38:\t\t is a more relaxed mode, but it generates more instrumentation code and\n 39:\t\t may potentially report errors in corner cases when non-instrumented\n 40:\t\t functions call instrumented ones.\n"
} |
| 47/2 | 2026/10/09 09:36 | llm | patch-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 34357 output: 24 thoughts: 375 Thoughts: **My Assessment of KMSAN Requirements for Memory Management Changes**
Okay, so I'm digging into these changes in `mm/vmalloc.c` and `mm/percpu-vm.c`. The immediate question is, do I need to worry about KMSAN for testing these? No, right? These are core kernel memory management components that are enabled by default on amd64, and the MMU is pretty standard now.
But wait, hold on a second... Could `HAVE_ARCH_HUGE_VMALLOC` come into play here? It's worth a look. Let's see what that macro is doing. Looking at the code in `mm/vmalloc.c`, I see:
```c
if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
page_shift == PAGE_SHIFT) {
err = vmap_small_pages_range_noflush(addr, end, prot, pages);
} else {
for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
err = vmap_range_noflush(addr, addr + (1UL << page_shift),
page_to_phys(pages[i]), prot,
page_shift);
if (err)
break;
addr += 1UL << page_shift;
}
}
/* Undo the PTEs installed before the failure. */
if (err)
__vunmap_range_noflush(start, end);
```
Ah, it seems to be related to huge vmalloc pages. That `else` block is clearly handling the case where huge pages are involved. So, let's track down where `HAVE_ARCH_HUGE_VMALLOC` is defined. Specifically, on x86/amd64 systems. Let me check `arch/x86/Kconfig`.
|
| 48/2 | 2026/10/09 09:36 | tool | grepper |
0mArgs:{
"Expression": "HAVE_ARCH_HUGE_VMALLOC"
}Results: {
"Output": "arch/Kconfig=1101=config HAVE_ARCH_HUGE_VMAP\n--\narch/Kconfig-1108-#\narch/Kconfig:1109:config HAVE_ARCH_HUGE_VMALLOC\narch/Kconfig-1110-\tdepends on HAVE_ARCH_HUGE_VMAP\n--\narch/arm64/Kconfig=2=config ARM64\n--\narch/arm64/Kconfig-153-\tselect HAVE_ARCH_COMPILER_H\narch/arm64/Kconfig:154:\tselect HAVE_ARCH_HUGE_VMALLOC\narch/arm64/Kconfig-155-\tselect HAVE_ARCH_HUGE_VMAP\n--\narch/powerpc/Kconfig=118=config PPC\n--\narch/powerpc/Kconfig-218-\tselect HAVE_ARCH_AUDITSYSCALL\narch/powerpc/Kconfig:219:\tselect HAVE_ARCH_HUGE_VMALLOC\t\tif HAVE_ARCH_HUGE_VMAP\narch/powerpc/Kconfig-220-\tselect HAVE_ARCH_HUGE_VMAP\t\tif PPC_RADIX_MMU || PPC_8xx\n--\narch/riscv/Kconfig=13=config RISCV\n--\narch/riscv/Kconfig-133-\tselect HAVE_ARCH_BITREVERSE if RISCV_ISA_ZBKB \u0026\u0026 BITREVERSE\narch/riscv/Kconfig:134:\tselect HAVE_ARCH_HUGE_VMALLOC if HAVE_ARCH_HUGE_VMAP\narch/riscv/Kconfig-135-\tselect HAVE_ARCH_HUGE_VMAP if MMU \u0026\u0026 64BIT\n--\narch/x86/Kconfig=57=config X86\n--\narch/x86/Kconfig-193-\tselect HAVE_ARCH_HUGE_VMAP\t\tif X86_64 || X86_PAE\narch/x86/Kconfig:194:\tselect HAVE_ARCH_HUGE_VMALLOC\t\tif X86_64\narch/x86/Kconfig-195-\tselect HAVE_ARCH_JUMP_LABEL\n--\ninclude/linux/vmalloc.h=20=struct iov_iter;\t\t/* in uio.h */\n--\ninclude/linux/vmalloc.h-32-#define VM_MAP_PUT_PAGES\t0x00000200\t/* put pages and free array in vfree */\ninclude/linux/vmalloc.h:33:#define VM_ALLOW_HUGE_VMAP\t0x00000400 /* Allow for huge pages on archs with HAVE_ARCH_HUGE_VMALLOC */\ninclude/linux/vmalloc.h-34-\n--\ninclude/linux/vmalloc.h=54=struct vm_struct {\n--\ninclude/linux/vmalloc.h-63-\tstruct page\t\t**pages;\ninclude/linux/vmalloc.h:64:#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC\ninclude/linux/vmalloc.h-65-\tunsigned int\t\tpage_order;\n--\ninclude/linux/vmalloc.h=262=static inline bool is_vm_area_hugepages(const void *addr)\n--\ninclude/linux/vmalloc.h-270-\t */\ninclude/linux/vmalloc.h:271:#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC\ninclude/linux/vmalloc.h-272-\tstruct vm_struct *area = find_vm_area(addr);\n--\nmm/vmalloc.c=65=static const unsigned int ioremap_max_page_shift = PAGE_SHIFT;\n--\nmm/vmalloc.c-67-\nmm/vmalloc.c:68:#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC\nmm/vmalloc.c-69-static bool __ro_after_init vmap_allow_huge = true;\n--\nmm/vmalloc.c=76=early_param(\"nohugevmalloc\", set_nohugevmalloc);\nmm/vmalloc.c:77:#else /* CONFIG_HAVE_ARCH_HUGE_VMALLOC */\nmm/vmalloc.c-78-static const bool vmap_allow_huge = false;\nmm/vmalloc.c:79:#endif\t/* CONFIG_HAVE_ARCH_HUGE_VMALLOC */\nmm/vmalloc.c-80-\n--\nmm/vmalloc.c=685=int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-697-\nmm/vmalloc.c:698:\tif (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||\nmm/vmalloc.c-699-\t\t\tpage_shift == PAGE_SHIFT) {\n--\nmm/vmalloc.c=3193=static inline unsigned int vm_area_page_order(const struct vm_struct *vm)\nmm/vmalloc.c-3194-{\nmm/vmalloc.c:3195:#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC\nmm/vmalloc.c-3196-\treturn vm-\u003epage_order;\n--\nmm/vmalloc.c=3207=static inline void set_vm_area_page_order(struct vm_struct *vm, unsigned int order)\nmm/vmalloc.c-3208-{\nmm/vmalloc.c:3209:#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC\nmm/vmalloc.c-3210-\tvm-\u003epage_order = order;\n"
} |
| 49/2 | 2026/10/09 09:36 | llm | patch-evaluator |
1mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 36574 output: 221 thoughts: 8087 Thoughts: **Analysis of Kernel Patch for Memory Management** Okay, here's the breakdown. This patch is fundamentally about improving error handling in the vmalloc/vmap subsystem within the Linux kernel, specifically regarding the proper unmapping and cleanup of page table entries when these operations fail. My focus here is ensuring this patch gets the right fuzzing attention. First, I need to identify which configuration options are necessary for the modified code to be reachable. I've checked the Kconfig files and the code itself. The core changes are in `mm/vmalloc.c` and `mm/percpu-vm.c`, which are critical memory management components. *No* special configuration options are required to enable and reach this code on the target architecture (amd64) in standard virtualized fuzzing environments. These components depend on standard, always-on configurations like `CONFIG_MMU` which is selected by `CONFIG_X86_64`. The patch *also* touches `mm/kmsan/shadow.c`. This is where the code becomes interesting but potentially misleading. While the patch *does* modify this KMSAN-specific file, KMSAN itself is *not* a requirement to reach the *primary* code changes related to memory management. Enabling KMSAN would require a different build, and it also requires clang. Moreover, if KMSAN is selected in `EnableConfigs`, it breaks builds that use KASAN. Therefore, adding `KMSAN` to `EnableConfigs` would prevent the fuzzer from reaching the main code in `mm/vmalloc.c`. This means that `EnableConfigs` should be empty: `[]`. We want to ensure that the fuzzing effort is not diluted by forcing special configs. The crux of the matter is identifying the `FocusSymbols`. These must be functions that *specifically* implement or are *directly* impacted by the changes, avoiding ubiquitous, core lifecycle functions (like `kmalloc`, `kfree`, etc.). After carefully reviewing the code, I've determined that the following functions are the best candidates. The core functions modified are: * `__vmap_pages_range_noflush` * `vmap_pages_range_noflush` * `vmap_page_range` * `kmsan_vmap_pages_range_noflush` These are non-static functions directly impacted by changes in `mm/vmalloc.c` and `mm/kmsan/shadow.c` and are central to the error-handling improvements. Listing these functions ensures the fuzzer focuses on the *actual* logic being modified and the new assertions and error unwind logic added. The modifications to KMSAN are important for its shadow tracking, but not central to the core change about cleanup upon errors. The patch does not change core KMSAN logic. In summary, for effective fuzzing of this patch: * `WorthFuzzing=true` * `EnableConfigs: []` * `FocusSymbols: ["__vmap_pages_range_noflush", "vmap_pages_range_noflush", "vmap_page_range", "kmsan_vmap_pages_range_noflush"]` |
| 50/2 | 2026/10/09 09:38 | tool | set-results |
0mArgs:{
"EnableConfigs": [],
"FocusSymbols": [
"__vmap_pages_range_noflush",
"vmap_pages_range_noflush",
"vmap_page_range",
"kmsan_vmap_pages_range_noflush"
],
"Reasoning": "The patch alters core memory management code in mm/vmalloc.c, mm/percpu-vm.c, and mm/kmsan/shadow.c. It introduces new runtime assertions (WARN_ON_ONCE checks on address bounds and page shift) in __vmap_pages_range_noflush() and modifies error unwinding semantics so that partial page table mappings roll back automatically on failure across vmap_page_range(), __vmap_pages_range_noflush(), and kmsan_vmap_pages_range_noflush(). These code paths are reachable on amd64 in virtualized environments via standard vmalloc, vmap, and percpu allocations.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": null,
"FocusSymbols": [
"__vmap_pages_range_noflush",
"vmap_pages_range_noflush",
"vmap_page_range",
"kmsan_vmap_pages_range_noflush"
],
"Reasoning": "The patch alters core memory management code in mm/vmalloc.c, mm/percpu-vm.c, and mm/kmsan/shadow.c. It introduces new runtime assertions (WARN_ON_ONCE checks on address bounds and page shift) in __vmap_pages_range_noflush() and modifies error unwinding semantics so that partial page table mappings roll back automatically on failure across vmap_page_range(), __vmap_pages_range_noflush(), and kmsan_vmap_pages_range_noflush(). These code paths are reachable on amd64 in virtualized environments via standard vmalloc, vmap, and percpu allocations.",
"WorthFuzzing": true
} |
| 51/1 | 2026/10/09 09:38 | action | If |
1mArgs:{
"WorthFuzzing": true
}Results: null |
| 52/2 | 2026/10/09 09:38 | agent | kmsan-evaluator |
1mModel:core Args: null Results: {
"KMSANReasoning": "The patch series improves error handling and unwinding during kernel virtual memory mapping (vmalloc/ioremap/percpu/kmsan shadow). Specifically, it ensures that partially installed page tables and KMSAN shadow/origin metadata mappings are cleanly unwound and unmapped upon failure within `vmap_pages_range_noflush()`, `__vmap_pages_range_noflush()`, `vmap_page_range()`, and `kmsan_vmap_pages_range_noflush()`, and removes redundant cleanup in callers.\n\nThese changes deal strictly with kernel page table management, TLB invalidation, and error unwinding. They do not introduce or modify any kernel structures exposed to user space, nor do they introduce any logic reading or branching on uninitialized stack or heap variables. Any potential bugs in this patch (such as incorrect address ranges, double unmaps, or page table corruption) fall under general memory management / page table errors, which are checked by standard kernel asserts and KASAN builds. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"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 3eeb0ec9d1278ab64da2fcb0f06e870d40cc97bc
Author: syz-cluster <triage@syzkaller.com>
Date: Fri Oct 9 09:33:29 2026 +0000
syz-cluster: applied patch under review
diff --git a/arch/powerpc/kernel/isa-bridge.c b/arch/powerpc/kernel/isa-bridge.c
index 5c064485197a9..93029d85e6eaf 100644
--- a/arch/powerpc/kernel/isa-bridge.c
+++ b/arch/powerpc/kernel/isa-bridge.c
@@ -46,9 +46,8 @@ static void remap_isa_base(phys_addr_t pa, unsigned long size)
WARN_ON_ONCE(size & ~PAGE_MASK);
if (slab_is_available()) {
- if (vmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,
- pgprot_noncached(PAGE_KERNEL)))
- vunmap_range(ISA_IO_BASE, ISA_IO_BASE + size);
+ vmap_page_range(ISA_IO_BASE, ISA_IO_BASE + size, pa,
+ pgprot_noncached(PAGE_KERNEL));
} else {
early_ioremap_range(ISA_IO_BASE, pa, size,
pgprot_noncached(PAGE_KERNEL));
diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
index e27342ef128b8..f74269636d5ec 100644
--- a/arch/powerpc/kernel/pci_64.c
+++ b/arch/powerpc/kernel/pci_64.c
@@ -139,10 +139,8 @@ void __iomem *ioremap_phb(phys_addr_t paddr, unsigned long size)
addr = (unsigned long)area->addr;
if (ioremap_page_range(addr, addr + size, paddr,
- pgprot_noncached(PAGE_KERNEL))) {
- vunmap_range(addr, addr + size);
+ pgprot_noncached(PAGE_KERNEL)))
return NULL;
- }
return (void __iomem *)addr;
}
diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
index 0c88d89bf0d68..2166086d3dc3b 100644
--- a/mm/kmsan/shadow.c
+++ b/mm/kmsan/shadow.c
@@ -258,6 +258,10 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
o_pages, page_shift);
kmsan_leave_runtime();
if (mapped) {
+ /* Undo the shadow mapping set up above. */
+ kmsan_enter_runtime();
+ __vunmap_range_noflush(shadow_start, shadow_end);
+ kmsan_leave_runtime();
err = mapped;
goto ret;
}
diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
index 509d8901835cd..59d3a336a6bd1 100644
--- a/mm/percpu-vm.c
+++ b/mm/percpu-vm.c
@@ -252,10 +252,11 @@ static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages,
return 0;
err:
for_each_possible_cpu(tcpu) {
- __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
- page_end - page_start);
+ /* The failing CPU's partial mapping undoes itself */
if (tcpu == cpu)
break;
+ __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
+ page_end - page_start);
}
pcpu_post_unmap_tlb_flush(chunk, page_start, page_end);
return err;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index db669103dc666..e1b376f57dd25 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -363,6 +363,9 @@ int vmap_page_range(unsigned long addr, unsigned long end,
if (!err)
err = kmsan_ioremap_page_range(addr, end, phys_addr, prot,
ioremap_max_page_shift);
+ if (err)
+ __vunmap_range_noflush(addr, end);
+
return err;
}
@@ -683,27 +686,35 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
pgprot_t prot, struct page **pages, unsigned int page_shift)
{
unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
+ unsigned long start = addr;
+ int err = 0;
+
+ if (WARN_ON_ONCE(addr >= end))
+ return -EINVAL;
if (WARN_ON_ONCE(page_shift < PAGE_SHIFT))
return -EINVAL;
if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
- page_shift == PAGE_SHIFT)
- return vmap_small_pages_range_noflush(addr, end, prot, pages);
-
- for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
- int err;
-
- err = vmap_range_noflush(addr, addr + (1UL << page_shift),
+ page_shift == PAGE_SHIFT) {
+ err = vmap_small_pages_range_noflush(addr, end, prot, pages);
+ } else {
+ for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
+ err = vmap_range_noflush(addr, addr + (1UL << page_shift),
page_to_phys(pages[i]), prot,
page_shift);
- if (err)
- return err;
+ if (err)
+ break;
- addr += 1UL << page_shift;
+ addr += 1UL << page_shift;
+ }
}
- return 0;
+ /* Undo the PTEs installed before the failure. */
+ if (err)
+ __vunmap_range_noflush(start, end);
+
+ return err;
}
int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
@@ -715,7 +726,16 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
if (ret)
return ret;
- return __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+
+ ret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+ /*
+ * The page tables undo themselves on failure. Tear down the
+ * metadata that was fully set up before the mapping failed.
+ */
+ if (ret)
+ kmsan_vunmap_range_noflush(addr, end);
+
+ return ret;
}
static int __vmap_pages_range(unsigned long addr, unsigned long end,
|
| 53/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 4006 output: 21 thoughts: 720 Thoughts: **Analyzing the Potential Need for a Dedicated KMSAN Fuzzing Session** Okay, so the question is whether these code changes warrant a dedicated KMSAN fuzzing setup in addition to our standard KASAN efforts. Let's break this down. First, I need to get a clear picture of what's being modified. The patch touches `arch/powerpc/kernel/isa-bridge.c`, `arch/powerpc/kernel/pci_64.c`, `mm/kmsan/shadow.c`, `mm/percpu-vm.c`, and `mm/vmalloc.c`. Interesting. A mixed bag, but certainly related to memory management and potentially address space interactions. Now, let's dive into the code changes themselves, starting with `mm/kmsan/shadow.c`. It looks like `kmsan_vmap_pages_range_noflush` is involved, and it appears this function is handling the mapping of shadow and origin pages, especially for vmalloc ranges. The patch is adding `__vunmap_range_noflush` calls within `kmsan_vmap_pages_range_noflush`. In a failure scenario, the shadow mapping, set up before, is now undone. Moving on to `mm/vmalloc.c`, I see a clear pattern emerging. Functions like `vmap_page_range`, `__vmap_pages_range_noflush`, and `vmap_pages_range_noflush` are all getting cleanup logic added. Specifically, if a mapping operation fails, the patch introduces calls to `__vunmap_range_noflush` or `kmsan_vunmap_range_noflush` to roll back the partially established mappings. Essentially, if there is a failure, there is a mechanism to undo the damage. Then, there is the connection to `arch/powerpc/kernel/isa-bridge.c`, `pci_64.c`, and `mm/percpu-vm.c`. The changes mean that these modules no longer need to handle failure cleanup themselves. The functions they call (`vmap_pages_range`, `ioremap_page_range`) now take care of that. They are cleaning up after themselves. So, the underlying issue seems to be a more robust and self-contained error handling for page mapping and vmalloc failures, especially within the context of KMSAN. This indicates a potential race condition or vulnerability if there wasn't appropriate cleanup. It implies that these functions weren't correctly cleaning up memory or address space mappings on failure, leading to potential memory leaks, stale mappings, or even more severe corruption. Now, the crucial question. Does this necessitate dedicated KMSAN fuzzing? My initial instinct is that this *might* increase the likelihood of KMSAN catching something. The patch is improving KMSAN's ability to detect failures related to page mapping. The new cleanup logic should make things safer, but it also means KMSAN is now directly involved in these failure paths. Therefore, a deeper analysis into the bug that the changes fix is in order. I need to find the commit message or related issues to understand the exact vulnerability being addressed. Then I can determine if this is a high-risk area. |
| 54/3 | 2026/10/09 09:38 | tool | grepper |
0mArgs:{
"Expression": "Undo the shadow mapping set up above"
}Results: {
"Output": "mm/kmsan/shadow.c=217=int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,\n--\nmm/kmsan/shadow.c-260-\tif (mapped) {\nmm/kmsan/shadow.c:261:\t\t/* Undo the shadow mapping set up above. */\nmm/kmsan/shadow.c-262-\t\tkmsan_enter_runtime();\n"
} |
| 55/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 5545 output: 36 thoughts: 21 Thoughts: Here's my summary, as if I were thinking these thoughts: **Analyzing the Memory Sanitizer Shadow Memory Implementation** Okay, time to dive into the nitty-gritty. Let's start by zeroing in on `mm/kmsan/shadow.c`, specifically around line 217. I'm guessing that's where a critical piece of the shadow memory management is taking place. This is where the magic (or the potential headaches) of KMSAN is probably implemented. I need to understand exactly what that code is doing. Perhaps memory mapping or something crucial to pointer arithmetic is happening there. My goal is to grasp how the "shadow" is kept in sync with the real memory, and where the potential bottlenecks or areas for improvement might be in terms of performance or even how it handles tricky concurrency situations. |
| 56/3 | 2026/10/09 09:38 | tool | read-file |
0mArgs:{
"File": "mm/kmsan/shadow.c",
"FirstLine": 215,
"LineCount": 60
}Results: {
"Contents": " 215:\t}\n 216:\t\n 217:\tint kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,\n 218:\t\t\t\t\t pgprot_t prot, struct page **pages,\n 219:\t\t\t\t\t unsigned int page_shift, gfp_t gfp_mask)\n 220:\t{\n 221:\t\tunsigned long shadow_start, origin_start, shadow_end, origin_end;\n 222:\t\tstruct page **s_pages, **o_pages;\n 223:\t\tint nr, mapped, err = 0;\n 224:\t\n 225:\t\tif (!kmsan_enabled)\n 226:\t\t\treturn 0;\n 227:\t\n 228:\t\tshadow_start = vmalloc_meta((void *)start, KMSAN_META_SHADOW);\n 229:\t\tshadow_end = vmalloc_meta((void *)end, KMSAN_META_SHADOW);\n 230:\t\tif (!shadow_start)\n 231:\t\t\treturn 0;\n 232:\t\n 233:\t\tnr = (end - start) / PAGE_SIZE;\n 234:\t\ts_pages = kzalloc_objs(*s_pages, nr, gfp_mask);\n 235:\t\to_pages = kzalloc_objs(*o_pages, nr, gfp_mask);\n 236:\t\tif (!s_pages || !o_pages) {\n 237:\t\t\terr = -ENOMEM;\n 238:\t\t\tgoto ret;\n 239:\t\t}\n 240:\t\tfor (int i = 0; i \u003c nr; i++) {\n 241:\t\t\ts_pages[i] = shadow_page_for(pages[i]);\n 242:\t\t\to_pages[i] = origin_page_for(pages[i]);\n 243:\t\t}\n 244:\t\tprot = PAGE_KERNEL;\n 245:\t\n 246:\t\torigin_start = vmalloc_meta((void *)start, KMSAN_META_ORIGIN);\n 247:\t\torigin_end = vmalloc_meta((void *)end, KMSAN_META_ORIGIN);\n 248:\t\tkmsan_enter_runtime();\n 249:\t\tmapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,\n 250:\t\t\t\t\t\t s_pages, page_shift);\n 251:\t\tkmsan_leave_runtime();\n 252:\t\tif (mapped) {\n 253:\t\t\terr = mapped;\n 254:\t\t\tgoto ret;\n 255:\t\t}\n 256:\t\tkmsan_enter_runtime();\n 257:\t\tmapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,\n 258:\t\t\t\t\t\t o_pages, page_shift);\n 259:\t\tkmsan_leave_runtime();\n 260:\t\tif (mapped) {\n 261:\t\t\t/* Undo the shadow mapping set up above. */\n 262:\t\t\tkmsan_enter_runtime();\n 263:\t\t\t__vunmap_range_noflush(shadow_start, shadow_end);\n 264:\t\t\tkmsan_leave_runtime();\n 265:\t\t\terr = mapped;\n 266:\t\t\tgoto ret;\n 267:\t\t}\n 268:\t\tflush_tlb_kernel_range(shadow_start, shadow_end);\n 269:\t\tflush_tlb_kernel_range(origin_start, origin_end);\n 270:\t\tflush_cache_vmap(shadow_start, shadow_end);\n 271:\t\tflush_cache_vmap(origin_start, origin_end);\n 272:\t\n 273:\tret:\n 274:\t\tkfree(s_pages);\n"
} |
| 57/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 6768 output: 34 thoughts: 24 Thoughts: Here's my take on the thought process: **Diving into the Memory Allocation Plumbing** Okay, so I need to get to the bottom of this. My instincts are telling me to look at `mm/vmalloc.c`. This is where the kernel's virtual memory allocation routines live, and it's a likely spot for the issue I'm chasing. Now, I'm thinking specifically around lines 715 and 363. Those areas are often key for understanding how `vmalloc` is working in detail and could hold the critical code paths I need to examine. I'll need to see what's happening there with the relevant data structures and control flow. Time to get my hands dirty. |
| 58/3 | 2026/10/09 09:38 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 355,
"LineCount": 40
}Results: {
"Contents": " 355:\tint vmap_page_range(unsigned long addr, unsigned long end,\n 356:\t\t\t phys_addr_t phys_addr, pgprot_t prot)\n 357:\t{\n 358:\t\tint err;\n 359:\t\n 360:\t\terr = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot),\n 361:\t\t\t\t\t ioremap_max_page_shift);\n 362:\t\tflush_cache_vmap(addr, end);\n 363:\t\tif (!err)\n 364:\t\t\terr = kmsan_ioremap_page_range(addr, end, phys_addr, prot,\n 365:\t\t\t\t\t\t ioremap_max_page_shift);\n 366:\t\tif (err)\n 367:\t\t\t__vunmap_range_noflush(addr, end);\n 368:\t\n 369:\t\treturn err;\n 370:\t}\n 371:\t\n 372:\tint ioremap_page_range(unsigned long addr, unsigned long end,\n 373:\t\t\tphys_addr_t phys_addr, pgprot_t prot)\n 374:\t{\n 375:\t\tstruct vm_struct *area;\n 376:\t\n 377:\t\tarea = find_vm_area((void *)addr);\n 378:\t\tif (!area || !(area-\u003eflags \u0026 VM_IOREMAP)) {\n 379:\t\t\tWARN_ONCE(1, \"vm_area at addr %lx is not marked as VM_IOREMAP\\n\", addr);\n 380:\t\t\treturn -EINVAL;\n 381:\t\t}\n 382:\t\tif (addr != (unsigned long)area-\u003eaddr ||\n 383:\t\t (void *)end != area-\u003eaddr + get_vm_area_size(area)) {\n 384:\t\t\tWARN_ONCE(1, \"ioremap request [%lx,%lx) doesn't match vm_area [%lx, %lx)\\n\",\n 385:\t\t\t\t addr, end, (long)area-\u003eaddr,\n 386:\t\t\t\t (long)area-\u003eaddr + get_vm_area_size(area));\n 387:\t\t\treturn -ERANGE;\n 388:\t\t}\n 389:\t\treturn vmap_page_range(addr, end, phys_addr, prot);\n 390:\t}\n 391:\t\n 392:\tstatic void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,\n 393:\t\t\t\t pgtbl_mod_mask *mask)\n 394:\t{\n"
} |
| 59/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 7670 output: 34 thoughts: 25 Thoughts: Okay, let's dive into this. Here's my take on those lines: **Analyzing `mm/vmalloc.c` (Lines 700-760)** Right, I need to get a clear picture of what's happening within that region of the `vmalloc` code. Let's see...I'm assuming this section deals with a specific aspect of virtual memory allocation. Going in with the understanding that I'm looking for the allocation process, how are they handling the different cases, maybe the protection flags, perhaps also looking at the kernel addresses. I need to understand the details that surround the code. What allocation strategy are they implementing? Is it the initial setup, a retry mechanism after failure, or handling of page table entries? Are there potential areas for contention or optimization I should be aware of, given my knowledge of the system? I'll be looking specifically at the logic flow within those lines, the data structures being manipulated, and any conditional checks that influence the allocation process. I should also note any calls to other functions here. |
| 60/3 | 2026/10/09 09:38 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 705,
"LineCount": 55
}Results: {
"Contents": " 705:\t\t\t\t\t\tpage_shift);\n 706:\t\t\t\tif (err)\n 707:\t\t\t\t\tbreak;\n 708:\t\n 709:\t\t\t\taddr += 1UL \u003c\u003c page_shift;\n 710:\t\t\t}\n 711:\t\t}\n 712:\t\n 713:\t\t/* Undo the PTEs installed before the failure. */\n 714:\t\tif (err)\n 715:\t\t\t__vunmap_range_noflush(start, end);\n 716:\t\n 717:\t\treturn err;\n 718:\t}\n 719:\t\n 720:\tint vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n 721:\t\t\tpgprot_t prot, struct page **pages, unsigned int page_shift,\n 722:\t\t\tgfp_t gfp_mask)\n 723:\t{\n 724:\t\tint ret = kmsan_vmap_pages_range_noflush(addr, end, prot, pages,\n 725:\t\t\t\t\t\t\tpage_shift, gfp_mask);\n 726:\t\n 727:\t\tif (ret)\n 728:\t\t\treturn ret;\n 729:\t\n 730:\t\tret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);\n 731:\t\t/*\n 732:\t\t * The page tables undo themselves on failure. Tear down the\n 733:\t\t * metadata that was fully set up before the mapping failed.\n 734:\t\t */\n 735:\t\tif (ret)\n 736:\t\t\tkmsan_vunmap_range_noflush(addr, end);\n 737:\t\n 738:\t\treturn ret;\n 739:\t}\n 740:\t\n 741:\tstatic int __vmap_pages_range(unsigned long addr, unsigned long end,\n 742:\t\t\tpgprot_t prot, struct page **pages, unsigned int page_shift,\n 743:\t\t\tgfp_t gfp_mask)\n 744:\t{\n 745:\t\tint err;\n 746:\t\n 747:\t\terr = vmap_pages_range_noflush(addr, end, prot, pages, page_shift, gfp_mask);\n 748:\t\tflush_cache_vmap(addr, end);\n 749:\t\treturn err;\n 750:\t}\n 751:\t\n 752:\t/**\n 753:\t * vmap_pages_range - map pages to a kernel virtual address\n 754:\t * @addr: start of the VM area to map\n 755:\t * @end: end of the VM area to map (non-inclusive)\n 756:\t * @prot: page protection flags to use\n 757:\t * @pages: pages to map (always PAGE_SIZE pages)\n 758:\t * @page_shift: maximum shift that the pages may be mapped with, @pages must\n 759:\t * be aligned and contiguous up to at least this shift.\n"
} |
| 61/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 8755 output: 36 thoughts: 25 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Diving into `pcpu_map_pages`** Alright, let's refresh our memory on `pcpu_map_pages` and how it works, and I want to zero in on how it's implemented in `mm/percpu-vm.c`. I know the underlying principle: it maps pages, likely in a per-CPU context, but the specifics are where the real interest lies. I'm keen to see how the code handles the nuances of mapping, especially with per-CPU memory pools. I'll be looking for how it deals with the allocation or selection of physical pages, if it uses any specific mechanisms for tracking per-CPU mappings, and how it handles potential race conditions or synchronization issues in a multi-CPU environment. I expect to be looking for details regarding the potential implications of NUMA configurations in relation to this operation. I'll need to understand if this function supports any level of fault tolerance, and if so, how. Any usage of specific data structures, like page tables or per-cpu data, will be of particular interest. Also, if there are any specific performance optimization strategies used, I'll be sure to identify them. I am going to make some guesses about what I will see, based on my previous understanding of similar functions. But let's see what's actually under the hood. Time to dig in! |
| 62/3 | 2026/10/09 09:38 | tool | read-file |
0mArgs:{
"File": "mm/percpu-vm.c",
"FirstLine": 240,
"LineCount": 35
}Results: {
"Contents": " 240:\t\n 241:\t\tfor_each_possible_cpu(cpu) {\n 242:\t\t\terr = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),\n 243:\t\t\t\t\t \u0026pages[pcpu_page_idx(cpu, page_start)],\n 244:\t\t\t\t\t page_end - page_start, gfp);\n 245:\t\t\tif (err \u003c 0)\n 246:\t\t\t\tgoto err;\n 247:\t\n 248:\t\t\tfor (i = page_start; i \u003c page_end; i++)\n 249:\t\t\t\tpcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],\n 250:\t\t\t\t\t\t chunk);\n 251:\t\t}\n 252:\t\treturn 0;\n 253:\terr:\n 254:\t\tfor_each_possible_cpu(tcpu) {\n 255:\t\t\t/* The failing CPU's partial mapping undoes itself */\n 256:\t\t\tif (tcpu == cpu)\n 257:\t\t\t\tbreak;\n 258:\t\t\t__pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),\n 259:\t\t\t\t\t page_end - page_start);\n 260:\t\t}\n 261:\t\tpcpu_post_unmap_tlb_flush(chunk, page_start, page_end);\n 262:\t\treturn err;\n 263:\t}\n 264:\t\n 265:\t/**\n 266:\t * pcpu_post_map_flush - flush cache after mapping\n 267:\t * @chunk: pcpu_chunk the regions to be flushed belong to\n 268:\t * @page_start: page index of the first page to be flushed\n 269:\t * @page_end: page index of the last page to be flushed + 1\n 270:\t *\n 271:\t * Pages [@page_start,@page_end) of @chunk have been mapped. Flush\n 272:\t * cache.\n 273:\t *\n 274:\t * As with pcpu_pre_unmap_flush(), TLB flushing also is done at once\n"
} |
| 63/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 9705 output: 22 thoughts: 240 Thoughts: **Investigating a KMSAN Shadowing Change** Okay, so I see this patch and immediately my attention is drawn to the fact that it's touching `mm/kmsan/shadow.c`. That's unusual. I need to understand *why* it's modifying the KMSAN shadow memory mapping. Let's dig in. Aha, it seems like the issue is related to `kmsan_vmap_pages_range_noflush`. Looking at the code snippet, it looks like it's mapping and unmapping ranges, specifically dealing with `shadow_start`, `shadow_end`, and the `origin_start` and `origin_end` regions. There's a call to `__vmap_pages_range_noflush` for both the shadow region and the original region. And there's some conditional unmapping of the shadow region using `__vunmap_range_noflush` if mapping the original region fails. That screams potential race condition or some subtle memory management interaction, especially considering the `kmsan_enter_runtime()` and `kmsan_leave_runtime()` calls around the unmap. Now, before jumping to conclusions, I need to know what `kmsan_vmap_pages_range_noflush` was doing *before* this patch. What was the *original* behavior? Understanding the baseline is absolutely crucial for evaluating the impact and purpose of this change. I'll need to go to the git history and track down the relevant commits, hopefully finding something that explains the initial design and the rationale for the shadowing setup in the first place. This is where I can start building a solid understanding of this patch's impact. |
| 64/3 | 2026/10/09 09:38 | tool | grepper |
0mError:no matches Args: {
"Expression": "vmap_pages_range.*Undo"
}Results: {
"error": "no matches"
} |
| 65/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 10335 output: 25 thoughts: 265 Thoughts: **Analyzing the vmap_pages_range_noflush Function**
Okay, let's dive into this `__vmap_pages_range_noflush` function and trace its behavior. First, I need to understand its original logic. From what I see in the code:
```c
if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
page_shift == PAGE_SHIFT)
return vmap_small_pages_range_noflush(addr, end, prot, pages);
for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
int err;
err = vmap_range_noflush(addr, addr + (1UL << page_shift),
page_to_phys(pages[i]), prot,
page_shift);
if (err)
return err;
addr += 1UL << page_shift;
}
return 0;
```
It seems the function employs different strategies based on whether the architecture supports huge vmalloc areas and if the page shift matches the base page size. If it's not a huge vmalloc or the page shift is the standard page size, it delegates to `vmap_small_pages_range_noflush`. Otherwise, it iterates through pages, mapping them in ranges defined by `page_shift` using `vmap_range_noflush`.
Now, the critical question is what happens if either `vmap_range_noflush` fails midway through the loop, or `vmap_small_pages_range_noflush` fails. This is where things get interesting and where a deeper understanding of the individual functions is needed to ensure robustness. I'll need to go and investigate what `vmap_small_pages_range_noflush` does and how it handles potential errors.
|
| 66/3 | 2026/10/09 09:38 | tool | grepper |
0mArgs:{
"Expression": "vmap_small_pages_range_noflush"
}Results: {
"Output": "mm/vmalloc.c=631=static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr,\n--\nmm/vmalloc.c-648-\nmm/vmalloc.c:649:static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\nmm/vmalloc.c-650-\t\tpgprot_t prot, struct page **pages)\n--\nmm/vmalloc.c=685=int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,\n--\nmm/vmalloc.c-699-\t\t\tpage_shift == PAGE_SHIFT) {\nmm/vmalloc.c:700:\t\terr = vmap_small_pages_range_noflush(addr, end, prot, pages);\nmm/vmalloc.c-701-\t} else {\n"
} |
| 67/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 11270 output: 34 thoughts: 17 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and delivered as a first-person summary: **Digging into `vmap_small_pages_range_noflush`** Alright, time to get my hands dirty. Let's see... the `vmap_small_pages_range_noflush` function. Right, it's that crucial piece of the puzzle dealing with the virtual mapping of small pages, and the "noflush" suffix has my attention immediately. I assume this means we're dealing with a specific optimization or a variation on the standard virtual mapping strategy where cache flushes are deliberately suppressed or minimized during the mapping process. My intuition is that this is likely tied to performance gains, perhaps in scenarios where we can guarantee some level of consistency or coherence without incurring the full cost of a flush. So, I'm thinking, what are the specific use cases driving the "noflush" behavior? Is this for ephemeral mappings? Maybe it's for mappings within a critical section where we're managing coherency explicitly at a higher level? Perhaps it's geared toward a particular memory allocator strategy or specific hardware configuration, and the "noflush" allows for some clever optimization to shave off cycles in mapping. I'll need to dig into the surrounding code to determine the contexts in which this is used. It's also worth investigating how it interacts with different caching modes and whether it introduces any potential race conditions or coherency concerns under specific circumstances. The goal is to thoroughly understand where and when it’s safe to avoid flushing, and what safeguards are in place. Now, let's trace this function and understand its implications. |
| 68/3 | 2026/10/09 09:38 | tool | read-file |
0mArgs:{
"File": "mm/vmalloc.c",
"FirstLine": 645,
"LineCount": 40
}Results: {
"Contents": " 645:\t\t} while (p4d++, addr = next, addr != end);\n 646:\t\treturn 0;\n 647:\t}\n 648:\t\n 649:\tstatic int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,\n 650:\t\t\tpgprot_t prot, struct page **pages)\n 651:\t{\n 652:\t\tunsigned long start = addr;\n 653:\t\tpgd_t *pgd;\n 654:\t\tunsigned long next;\n 655:\t\tint err = 0;\n 656:\t\tint nr = 0;\n 657:\t\tpgtbl_mod_mask mask = 0;\n 658:\t\n 659:\t\tBUG_ON(addr \u003e= end);\n 660:\t\tpgd = pgd_offset_k(addr);\n 661:\t\tdo {\n 662:\t\t\tnext = pgd_addr_end(addr, end);\n 663:\t\t\tif (pgd_bad(*pgd))\n 664:\t\t\t\tmask |= PGTBL_PGD_MODIFIED;\n 665:\t\t\terr = vmap_pages_p4d_range(pgd, addr, next, prot, pages, \u0026nr, \u0026mask);\n 666:\t\t\tif (err)\n 667:\t\t\t\tbreak;\n 668:\t\t} while (pgd++, addr = next, addr != end);\n 669:\t\n 670:\t\tif (mask \u0026 ARCH_PAGE_TABLE_SYNC_MASK)\n 671:\t\t\tarch_sync_kernel_mappings(start, end);\n 672:\t\n 673:\t\treturn err;\n 674:\t}\n 675:\t\n 676:\t/*\n 677:\t * vmap_pages_range_noflush is similar to vmap_pages_range, but does not\n 678:\t * flush caches.\n 679:\t *\n 680:\t * The caller is responsible for calling flush_cache_vmap() after this\n 681:\t * function returns successfully and before the addresses are accessed.\n 682:\t *\n 683:\t * This is an internal function only. Do not use outside mm/.\n 684:\t */\n"
} |
| 69/3 | 2026/10/09 09:38 | llm | kmsan-evaluator |
0mModel:gemini-3.8-flash Args: null Results: null Tokens: input: 12267 output: 248 thoughts: 3119 Thoughts: **Analysis of the Proposed Patch Series** Okay, so I've carefully reviewed this patch series. My initial thought was, "Hey, this is touching KMSAN's internals, maybe we need a dedicated KMSAN session?" But then I remembered the rule: KMSAN is for *uninitialized memory* risks that aren't caught by KASAN, LOCKDEP, or standard detectors. This patch mostly deals with error handling and cleanup, particularly in virtual memory mapping (`vmalloc.c`, `percpu-vm.c`) and page table management and shadow metadata (`mm/kmsan/shadow.c`). I went through the code and specifically looked for these KMSAN-triggering scenarios: kernel structures going to userspace with uninitialized fields, conditional logic depending on uninitialized variables, allocation of complex data structures with later uninitialized reads, or bounds checks that expose uninitialized bytes. Nothing. This patch is about *ensuring* proper cleanup after mapping failures: fixing potential leaks of page tables or KMSAN metadata. If a mapping fails, this patch *ensures* the allocation *fails*, and no vaddr range is given to callers! Thus no reads of uninitialized memory. The patch's changes fall squarely into the category of memory management/page table logic and ensuring no memory leaks occur, not creating uninitialized memory risks. The patch fixes issues like partially mapped page tables or dangling KMSAN shadow mappings upon errors. These kinds of bugs are detectable by KASAN/page fault/standard debugging. I went through the list again: * `arch/powerpc/kernel/isa-bridge.c` and `arch/powerpc/kernel/pci_64.c`: removes redundant error handling cleanup. * `mm/kmsan/shadow.c`: Cleanly unmaps KMSAN shadow pages after origin mapping failures. * `mm/percpu-vm.c`: improved error cleanup handling. * `mm/vmalloc.c`: Adds error cleanup in `vmap_page_range`, `__vmap_pages_range_noflush`, and `vmap_pages_range_noflush`. The core logic is all about *preventing* resource leaks and ensuring clean error paths, not introducing any uninitialized memory risks. Since this patch is NOT introducing memory leaks, I'm confident in setting `NeedsKMSAN=false`. The risk is out-of-bounds access, double unmapping, page table corruption, but not uninitialized memory issues. A dedicated KMSAN session is not necessary for this patch series. |
| 70/3 | 2026/10/09 09:39 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch series improves error handling and unwinding during kernel virtual memory mapping (vmalloc/ioremap/percpu/kmsan shadow). Specifically, it ensures that partially installed page tables and KMSAN shadow/origin metadata mappings are cleanly unwound and unmapped upon failure within `vmap_pages_range_noflush()`, `__vmap_pages_range_noflush()`, `vmap_page_range()`, and `kmsan_vmap_pages_range_noflush()`, and removes redundant cleanup in callers.\n\nThese changes deal strictly with kernel page table management, TLB invalidation, and error unwinding. They do not introduce or modify any kernel structures exposed to user space, nor do they introduce any logic reading or branching on uninitialized stack or heap variables. Any potential bugs in this patch (such as incorrect address ranges, double unmaps, or page table corruption) fall under general memory management / page table errors, which are checked by standard kernel asserts and KASAN builds. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch series improves error handling and unwinding during kernel virtual memory mapping (vmalloc/ioremap/percpu/kmsan shadow). Specifically, it ensures that partially installed page tables and KMSAN shadow/origin metadata mappings are cleanly unwound and unmapped upon failure within `vmap_pages_range_noflush()`, `__vmap_pages_range_noflush()`, `vmap_page_range()`, and `kmsan_vmap_pages_range_noflush()`, and removes redundant cleanup in callers.\n\nThese changes deal strictly with kernel page table management, TLB invalidation, and error unwinding. They do not introduce or modify any kernel structures exposed to user space, nor do they introduce any logic reading or branching on uninitialized stack or heap variables. Any potential bugs in this patch (such as incorrect address ranges, double unmaps, or page table corruption) fall under general memory management / page table errors, which are checked by standard kernel asserts and KASAN builds. Therefore, a dedicated KMSAN fuzzing session is not warranted.",
"NeedsKMSAN": false
} |
| Total Calls | Total Tokens | Avg Tokens | Total Duration (Seconds) | Avg Duration (Seconds) |
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| Total Calls | Total Duration (Seconds) | Avg Duration (Seconds) |
|---|