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CVE-2026-46008

Estado: AnalizadaMedia (4.7)—

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: fix damos_walk() vs kdamond_fn() exit race

When kdamond_fn() main loop is finished, the function cancels remaining damos_walk() request and unset the damon_ctx->kdamond so that API callers and API functions themselves can show the context is terminated. damos_walk() 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, damos_walk() starts waiting for the kdamond's handling of the newly added request.

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The damos_walk() requests registration and damon_ctx->kdamond unset are protected by different mutexes, though. Hence, damos_walk() could race with damon_ctx->kdamond unset, and result in deadlocks.

For example, let's suppose kdamond successfully finished the damow_walk() request cancelling. Right after that, damos_walk() 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 damos_walk() 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 damos_walk() caller thread infinitely waits.

Fix this by introducing another damon_ctx field, namely walk_control_obsolete. It is protected by the damon_ctx->walk_control_lock, which protects damos_walk() request registration. Initialize (unset) it in kdamond_fn() before letting damon_start() returns and set it just before the cancelling of the remaining damos_walk() request is executed. damos_walk() 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.

The issue is found by sashiko [1].

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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        "source": "nvd@nist.gov",
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          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
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    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/core: fix damos_walk() vs kdamond_fn() exit race\n\nWhen kdamond_fn() main loop is finished, the function cancels remaining\ndamos_walk() request and unset the damon_ctx->kdamond so that API callers\nand API functions themselves can show the context is terminated. \ndamos_walk() adds the caller's request to the queue first.  After that, it\nshows if the kdamond of the damon_ctx is still running (damon_ctx->kdamond\nis set).  Only if the kdamond is running, damos_walk() starts waiting for\nthe kdamond's handling of the newly added request.\n\nThe damos_walk() requests registration and damon_ctx->kdamond unset are\nprotected by different mutexes, though.  Hence, damos_walk() could race\nwith damon_ctx->kdamond unset, and result in deadlocks.\n\nFor example, let's suppose kdamond successfully finished the damow_walk()\nrequest cancelling.  Right after that, damos_walk() 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\ndamos_walk() 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 damos_walk() caller thread\ninfinitely waits.\n\nFix this by introducing another damon_ctx field, namely\nwalk_control_obsolete.  It is protected by the\ndamon_ctx->walk_control_lock, which protects damos_walk() request\nregistration.  Initialize (unset) it in kdamond_fn() before letting\ndamon_start() returns and set it just before the cancelling of the\nremaining damos_walk() request is executed.  damos_walk() reads the\nobsolete field under 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\nThe issue is found by sashiko [1]."
    }
  ],
  "lastModified": "2026-06-17T10:52:53.427",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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          "operator": "OR"
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  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}