mm/damon/core: clear walk_control on inactive context in damos_walk()

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Summary

CVECVE-2026-43388
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-08 15:16:50 UTC
Updated2026-05-12 14:10:27 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: mm/damon/core: clear walk_control on inactive context in damos_walk() damos_walk() sets ctx->walk_control to the caller-provided control structure before checking whether the context is running. If the context is inactive (damon_is_running() returns false), the function returns -EINVAL without clearing ctx->walk_control. This leaves a dangling pointer to a stack-allocated structure that will be freed when the caller returns. This is structurally identical to the bug fixed in commit f9132fbc2e83 ("mm/damon/core: remove call_control in inactive contexts") for damon_call(), which had the same pattern of linking a control object and returning an error without unlinking it. The dangling walk_control pointer can cause: 1. Use-after-free if the context is later started and kdamond    dereferences ctx->walk_control (e.g., in damos_walk_cancel()    which writes to control->canceled and calls complete()) 2. Permanent -EBUSY from subsequent damos_walk() calls, since the    stale pointer is non-NULL Nonetheless, the real user impact is quite restrictive. The use-after-free is impossible because there is no damos_walk() callers who starts the context later. The permanent -EBUSY can actually confuse users, as DAMON is not running. But the symptom is kept only while the context is turned off. Turning it on again will make DAMON internally uses a newly generated damon_ctx object that doesn't have the invalid damos_walk_control pointer, so everything will work fine again. Fix this by clearing ctx->walk_control under walk_control_lock before returning -EINVAL, mirroring the fix pattern from f9132fbc2e83.

Risk And Classification

EPSS: 0.000170000 probability, percentile 0.041320000 (date 2026-05-12)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61 ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b git Not specified
CNA Linux Linux affected bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61 9320c77134ab8d7701e20608bbf08517df4fa321 git Not specified
CNA Linux Linux affected bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61 d210fdcac9c0d1380eab448aebc93f602c1cd4e6 git Not specified
CNA Linux Linux affected 6.14 Not specified
CNA Linux Linux unaffected 6.14 semver Not specified
CNA Linux Linux unaffected 6.18.19 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.9 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9320c77134ab8d7701e20608bbf08517df4fa321 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d210fdcac9c0d1380eab448aebc93f602c1cd4e6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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