{"id":"CVE-2026-46025","state":"PUBLISHED","title":"mm/damon/core: fix damon_call() vs kdamond_fn() exit race","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/core: fix damon_call() vs kdamond_fn() exit race\n\nPatch series \"mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit\nrace\".\n\ndamon_call() and damos_walk() can leak memory and/or deadlock when they\nrace with kdamond terminations.  Fix those.\n\n\nThis patch (of 2);\n\nWhen kdamond_fn() main loop is finished, the function cancels all\nremaining damon_call() requests and unset the damon_ctx->kdamond so that\nAPI callers and API functions themselves can know the context is\nterminated.  damon_call() adds the caller's request to the queue first. \nAfter that, it shows if the kdamond of the damon_ctx is still running\n(damon_ctx->kdamond is set).  Only if the kdamond is running, damon_call()\nstarts waiting for the kdamond's handling of the newly added request.\n\nThe damon_call() requests registration and damon_ctx->kdamond unset are\nprotected by different mutexes, though.  Hence, damon_call() could race\nwith damon_ctx->kdamond unset, and result in deadlocks.\n\nFor example, let's suppose kdamond successfully finished the damon_call()\nrequests cancelling.  Right after that, damon_call() is called for the\ncontext.  It registers the new request, and shows the context is still\nrunning, because damon_ctx->kdamond unset is not yet done.  Hence the\ndamon_call() caller starts waiting for the handling of the request. \nHowever, the kdamond is already on the termination steps, so it never\nhandles the new request.  As a result, the damon_call() caller threads\ninfinitely waits.\n\nFix this by introducing another damon_ctx field, namely\ncall_controls_obsolete.  It is protected by the\ndamon_ctx->call_controls_lock, which protects damon_call() requests\nregistration.  Initialize (unset) it in kdamond_fn() before letting\ndamon_start() returns and set it just before the cancelling of remaining\ndamon_call() requests is executed.  damon_call() reads the obsolete field\nunder the lock and avoids adding a new request.\n\nAfter this change, only requests that are guaranteed to be handled or\ncancelled are registered.  Hence the after-registration DAMON context\ntermination check is no longer needed.  Remove it together.\n\nNote that the deadlock will not happen when damon_call() is called for\nrepeat mode request.  In tis case, damon_call() returns instead of waiting\nfor the handling when the request registration succeeds and it shows the\nkdamond is running.  However, if the request also has dealloc_on_cancel,\nthe request memory would be leaked.\n\nThe issue is found by sashiko [1].","publishedAt":"2026-05-27T12:56:31.784Z","updatedAt":"2026-06-14T17:48:48.849Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42b7491af14cbba2393329ce43d508a957bd94fa","status":"affected","lessThan":"2691332ad88b57179c38653e2cd613d5820a52cf","versionType":"git"},{"version":"42b7491af14cbba2393329ce43d508a957bd94fa","status":"affected","lessThan":"e6a053a6f4b5048746c49432a5cc5b79fe4695fe","versionType":"git"},{"version":"42b7491af14cbba2393329ce43d508a957bd94fa","status":"affected","lessThan":"55da81663b9642dd046b26dd6f1baddbcf337c1e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/damon.h","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":"6.18.27","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.4","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/damon.h","mm/damon/core.c"]}],"references":["https://git.kernel.org/stable/c/2691332ad88b57179c38653e2cd613d5820a52cf","https://git.kernel.org/stable/c/e6a053a6f4b5048746c49432a5cc5b79fe4695fe","https://git.kernel.org/stable/c/55da81663b9642dd046b26dd6f1baddbcf337c1e"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/46xxx/CVE-2026-46025.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-46025","state":"PUBLISHED","datePublished":"2026-05-27T12:56:31.784Z","dateUpdated":"2026-06-14T17:48:48.849Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-13T15:03:33.093Z"},"containers":{"cna":{"title":"mm/damon/core: fix damon_call() vs kdamond_fn() exit race","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/core: fix damon_call() vs kdamond_fn() exit race\n\nPatch series \"mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit\nrace\".\n\ndamon_call() and damos_walk() can leak memory and/or deadlock when they\nrace with kdamond terminations.  Fix those.\n\n\nThis patch (of 2);\n\nWhen kdamond_fn() main loop is finished, the function cancels all\nremaining damon_call() requests and unset the damon_ctx->kdamond so that\nAPI callers and API functions themselves can know the context is\nterminated.  damon_call() adds the caller's request to the queue first. \nAfter that, it shows if the kdamond of the damon_ctx is still running\n(damon_ctx->kdamond is set).  Only if the kdamond is running, damon_call()\nstarts waiting for the kdamond's handling of the newly added request.\n\nThe damon_call() requests registration and damon_ctx->kdamond unset are\nprotected by different mutexes, though.  Hence, damon_call() could race\nwith damon_ctx->kdamond unset, and result in deadlocks.\n\nFor example, let's suppose kdamond successfully finished the damon_call()\nrequests cancelling.  Right after that, damon_call() is called for the\ncontext.  It registers the new request, and shows the context is still\nrunning, because damon_ctx->kdamond unset is not yet done.  Hence the\ndamon_call() caller starts waiting for the handling of the request. \nHowever, the kdamond is already on the termination steps, so it never\nhandles the new request.  As a result, the damon_call() caller threads\ninfinitely waits.\n\nFix this by introducing another damon_ctx field, namely\ncall_controls_obsolete.  It is protected by the\ndamon_ctx->call_controls_lock, which protects damon_call() requests\nregistration.  Initialize (unset) it in kdamond_fn() before letting\ndamon_start() returns and set it just before the cancelling of remaining\ndamon_call() requests is executed.  damon_call() reads the obsolete field\nunder the lock and avoids adding a new request.\n\nAfter this change, only requests that are guaranteed to be handled or\ncancelled are registered.  Hence the after-registration DAMON context\ntermination check is no longer needed.  Remove it together.\n\nNote that the deadlock will not happen when damon_call() is called for\nrepeat mode request.  In tis case, damon_call() returns instead of waiting\nfor the handling when the request registration succeeds and it shows the\nkdamond is running.  However, if the request also has dealloc_on_cancel,\nthe request memory would be leaked.\n\nThe issue is found by sashiko [1]."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42b7491af14cbba2393329ce43d508a957bd94fa","status":"affected","lessThan":"2691332ad88b57179c38653e2cd613d5820a52cf","versionType":"git"},{"version":"42b7491af14cbba2393329ce43d508a957bd94fa","status":"affected","lessThan":"e6a053a6f4b5048746c49432a5cc5b79fe4695fe","versionType":"git"},{"version":"42b7491af14cbba2393329ce43d508a957bd94fa","status":"affected","lessThan":"55da81663b9642dd046b26dd6f1baddbcf337c1e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/damon.h","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":"6.18.27","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.4","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/linux/damon.h","mm/damon/core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2691332ad88b57179c38653e2cd613d5820a52cf"},{"url":"https://git.kernel.org/stable/c/e6a053a6f4b5048746c49432a5cc5b79fe4695fe"},{"url":"https://git.kernel.org/stable/c/55da81663b9642dd046b26dd6f1baddbcf337c1e"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-06-14T17:48:48.849Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18.27"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.0.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}