{"id":"CVE-2026-46025","summary":"mm/damon/core: fix damon_call() vs kdamond_fn() exit race","details":"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-\u003ekdamond 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-\u003ekdamond 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-\u003ekdamond unset are\nprotected by different mutexes, though.  Hence, damon_call() could race\nwith damon_ctx-\u003ekdamond 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-\u003ekdamond 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-\u003ecall_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].","modified":"2026-06-18T03:55:30.099056045Z","published":"2026-05-27T12:56:31.784Z","related":["openSUSE-SU-2026:10954-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46025.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2691332ad88b57179c38653e2cd613d5820a52cf"},{"type":"WEB","url":"https://git.kernel.org/stable/c/55da81663b9642dd046b26dd6f1baddbcf337c1e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e6a053a6f4b5048746c49432a5cc5b79fe4695fe"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46025.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46025"},{"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":"42b7491af14cbba2393329ce43d508a957bd94fa"},{"fixed":"2691332ad88b57179c38653e2cd613d5820a52cf"},{"fixed":"e6a053a6f4b5048746c49432a5cc5b79fe4695fe"},{"fixed":"55da81663b9642dd046b26dd6f1baddbcf337c1e"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-46025.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.18.27"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-46025.json"}}],"schema_version":"1.7.5"}