{"id":"CVE-2026-43388","state":"PUBLISHED","title":"mm/damon/core: clear walk_control on inactive context in damos_walk()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/core: clear walk_control on inactive context in damos_walk()\n\ndamos_walk() sets ctx->walk_control to the caller-provided control\nstructure before checking whether the context is running.  If the context\nis inactive (damon_is_running() returns false), the function returns\n-EINVAL without clearing ctx->walk_control.  This leaves a dangling\npointer to a stack-allocated structure that will be freed when the caller\nreturns.\n\nThis is structurally identical to the bug fixed in commit f9132fbc2e83\n(\"mm/damon/core: remove call_control in inactive contexts\") for\ndamon_call(), which had the same pattern of linking a control object and\nreturning an error without unlinking it.\n\nThe dangling walk_control pointer can cause:\n1. Use-after-free if the context is later started and kdamond\n   dereferences ctx->walk_control (e.g., in damos_walk_cancel()\n   which writes to control->canceled and calls complete())\n2. Permanent -EBUSY from subsequent damos_walk() calls, since the\n   stale pointer is non-NULL\n\nNonetheless, the real user impact is quite restrictive.  The\nuse-after-free is impossible because there is no damos_walk() callers who\nstarts the context later.  The permanent -EBUSY can actually confuse\nusers, as DAMON is not running.  But the symptom is kept only while the\ncontext is turned off.  Turning it on again will make DAMON internally\nuses a newly generated damon_ctx object that doesn't have the invalid\ndamos_walk_control pointer, so everything will work fine again.\n\nFix this by clearing ctx->walk_control under walk_control_lock before\nreturning -EINVAL, mirroring the fix pattern from f9132fbc2e83.","publishedAt":"2026-05-08T14:21:33.966Z","updatedAt":"2026-05-11T22:23:37.300Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61","status":"affected","lessThan":"ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b","versionType":"git"},{"version":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61","status":"affected","lessThan":"9320c77134ab8d7701e20608bbf08517df4fa321","versionType":"git"},{"version":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61","status":"affected","lessThan":"d210fdcac9c0d1380eab448aebc93f602c1cd4e6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/damon/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/damon/core.c"]}],"references":["https://git.kernel.org/stable/c/ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b","https://git.kernel.org/stable/c/9320c77134ab8d7701e20608bbf08517df4fa321","https://git.kernel.org/stable/c/d210fdcac9c0d1380eab448aebc93f602c1cd4e6"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43388.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43388","state":"PUBLISHED","datePublished":"2026-05-08T14:21:33.966Z","dateUpdated":"2026-05-11T22:23:37.300Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.006Z"},"containers":{"cna":{"title":"mm/damon/core: clear walk_control on inactive context in damos_walk()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/core: clear walk_control on inactive context in damos_walk()\n\ndamos_walk() sets ctx->walk_control to the caller-provided control\nstructure before checking whether the context is running.  If the context\nis inactive (damon_is_running() returns false), the function returns\n-EINVAL without clearing ctx->walk_control.  This leaves a dangling\npointer to a stack-allocated structure that will be freed when the caller\nreturns.\n\nThis is structurally identical to the bug fixed in commit f9132fbc2e83\n(\"mm/damon/core: remove call_control in inactive contexts\") for\ndamon_call(), which had the same pattern of linking a control object and\nreturning an error without unlinking it.\n\nThe dangling walk_control pointer can cause:\n1. Use-after-free if the context is later started and kdamond\n   dereferences ctx->walk_control (e.g., in damos_walk_cancel()\n   which writes to control->canceled and calls complete())\n2. Permanent -EBUSY from subsequent damos_walk() calls, since the\n   stale pointer is non-NULL\n\nNonetheless, the real user impact is quite restrictive.  The\nuse-after-free is impossible because there is no damos_walk() callers who\nstarts the context later.  The permanent -EBUSY can actually confuse\nusers, as DAMON is not running.  But the symptom is kept only while the\ncontext is turned off.  Turning it on again will make DAMON internally\nuses a newly generated damon_ctx object that doesn't have the invalid\ndamos_walk_control pointer, so everything will work fine again.\n\nFix this by clearing ctx->walk_control under walk_control_lock before\nreturning -EINVAL, mirroring the fix pattern from f9132fbc2e83."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61","status":"affected","lessThan":"ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b","versionType":"git"},{"version":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61","status":"affected","lessThan":"9320c77134ab8d7701e20608bbf08517df4fa321","versionType":"git"},{"version":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61","status":"affected","lessThan":"d210fdcac9c0d1380eab448aebc93f602c1cd4e6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/damon/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/damon/core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b"},{"url":"https://git.kernel.org/stable/c/9320c77134ab8d7701e20608bbf08517df4fa321"},{"url":"https://git.kernel.org/stable/c/d210fdcac9c0d1380eab448aebc93f602c1cd4e6"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:23:37.300Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.19.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}