{"id":"CVE-2026-43388","summary":"mm/damon/core: clear walk_control on inactive context in damos_walk()","details":"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-\u003ewalk_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-\u003ewalk_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-\u003ewalk_control (e.g., in damos_walk_cancel()\n   which writes to control-\u003ecanceled 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-\u003ewalk_control under walk_control_lock before\nreturning -EINVAL, mirroring the fix pattern from f9132fbc2e83.","modified":"2026-08-12T03:51:12.656905559Z","published":"2026-05-08T14:21:33.966Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43388.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/9320c77134ab8d7701e20608bbf08517df4fa321"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d210fdcac9c0d1380eab448aebc93f602c1cd4e6"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43388.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43388"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"bf0eaba0ff9c9c8e6fd58ddfa1a8b6df4b813f61"},{"fixed":"ce0aa47c963b8c3e5beace89e2b5a665a64b5b6b"},{"fixed":"9320c77134ab8d7701e20608bbf08517df4fa321"},{"fixed":"d210fdcac9c0d1380eab448aebc93f602c1cd4e6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43388.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.18.19"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43388.json"}}],"schema_version":"1.9.0"}