CVE-2026-46025 (GCVE-0-2026-46025)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:56 – Updated: 2026-06-14 17:48
VLAI
Title
mm/damon/core: fix damon_call() vs kdamond_fn() exit race
Summary
In the Linux kernel, the following vulnerability has been resolved: mm/damon/core: fix damon_call() vs kdamond_fn() exit race Patch series "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race". damon_call() and damos_walk() can leak memory and/or deadlock when they race with kdamond terminations. Fix those. This patch (of 2); When kdamond_fn() main loop is finished, the function cancels all remaining damon_call() requests and unset the damon_ctx->kdamond so that API callers and API functions themselves can know the context is terminated. damon_call() adds the caller's request to the queue first. After that, it shows if the kdamond of the damon_ctx is still running (damon_ctx->kdamond is set). Only if the kdamond is running, damon_call() starts waiting for the kdamond's handling of the newly added request. The damon_call() requests registration and damon_ctx->kdamond unset are protected by different mutexes, though. Hence, damon_call() could race with damon_ctx->kdamond unset, and result in deadlocks. For example, let's suppose kdamond successfully finished the damon_call() requests cancelling. Right after that, damon_call() is called for the context. It registers the new request, and shows the context is still running, because damon_ctx->kdamond unset is not yet done. Hence the damon_call() caller starts waiting for the handling of the request. However, the kdamond is already on the termination steps, so it never handles the new request. As a result, the damon_call() caller threads infinitely waits. Fix this by introducing another damon_ctx field, namely call_controls_obsolete. It is protected by the damon_ctx->call_controls_lock, which protects damon_call() requests registration. Initialize (unset) it in kdamond_fn() before letting damon_start() returns and set it just before the cancelling of remaining damon_call() requests is executed. damon_call() reads the obsolete field under the lock and avoids adding a new request. After this change, only requests that are guaranteed to be handled or cancelled are registered. Hence the after-registration DAMON context termination check is no longer needed. Remove it together. Note that the deadlock will not happen when damon_call() is called for repeat mode request. In tis case, damon_call() returns instead of waiting for the handling when the request registration succeeds and it shows the kdamond is running. However, if the request also has dealloc_on_cancel, the request memory would be leaked. The issue is found by sashiko [1].
Severity
4.7 (Medium)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 42b7491af14cbba2393329ce43d508a957bd94fa , < 2691332ad88b57179c38653e2cd613d5820a52cf (git)
Affected: 42b7491af14cbba2393329ce43d508a957bd94fa , < e6a053a6f4b5048746c49432a5cc5b79fe4695fe (git)
Affected: 42b7491af14cbba2393329ce43d508a957bd94fa , < 55da81663b9642dd046b26dd6f1baddbcf337c1e (git)
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Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.18.27 , ≤ 6.18.* (semver)
Unaffected: 7.0.4 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          "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-\u003ekdamond so that\nAPI callers and API functions themselves can know the context is\nterminated.  damon_call() adds the caller\u0027s 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\u0027s 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\u0027s 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]."
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    "dateReserved": "2026-05-13T15:03:33.093Z",
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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.  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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-06-28T06:45:53+00:00",
      "cve": "CVE-2026-46025",
      "id": "CVE-2026-46025",
      "initial_release_date": "2026-05-27T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mm/damon/core: fix damon_call() vs kdamond_fn() exit race",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46025.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-06-15T01:25:16Z",
      "cve": "CVE-2026-46025",
      "id": "CVE-2026-46025",
      "initial_release_date": "2026-05-28T03:54:10Z",
      "product_status:known_not_affected": "291",
      "product_status:recommended": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-46025",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-46025.json",
      "version": "5"
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}