GHSA-PR5P-X5RG-2942

Vulnerability from github – Published: 2026-11-03 12:31 – Updated: 2026-11-03 12:31
VLAI
Details

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

dm cache: fix issue with background work locking

dm cache used a rw_semaphore for background_work_lock. Write locks on rw_semaphores have strict owner semantics, but there was no guarantee that the process that locked background_work_lock was the same process that unlocked it. This can be easily seen using a kernel compiled with CONFIG_DEBUG_RWSEMS. Given a dm cache device , run: 'dmsetup suspend && dmsetup resume '. This will trigger a kernel warning:

DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))

triggered by cache_resume(). To fix this, switch from a rw_semaphore to a spinlock and a wait queue. dm cache already has a wait queue and associated counter, migration_wait and nr_allocated_migrations, that was getting woken up when background work was getting completed, but wasn't actually used by anything. This is replaced by the background_work queue and counter.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-99256"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-11-03T12:17:32Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ndm cache: fix issue with background work locking\n\ndm cache used a rw_semaphore for background_work_lock. Write locks on\nrw_semaphores have strict owner semantics, but there was no guarantee\nthat the process that locked background_work_lock was the same process\nthat unlocked it. This can be easily seen using a kernel compiled with\nCONFIG_DEBUG_RWSEMS. Given a dm cache device \u003ccache\u003e, run: \u0027dmsetup\nsuspend \u003ccache\u003e \u0026\u0026 dmsetup resume \u003ccache\u003e\u0027. This will trigger a kernel\nwarning:\n\nDEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) \u0026\u0026 !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))\n\ntriggered by cache_resume(). To fix this, switch from a rw_semaphore to\na spinlock and a wait queue. dm cache already has a wait queue and\nassociated counter, migration_wait and nr_allocated_migrations, that was\ngetting woken up when background work was getting completed, but wasn\u0027t\nactually used by anything. This is replaced by the background_work queue\nand counter.",
  "id": "GHSA-pr5p-x5rg-2942",
  "modified": "2026-11-03T12:31:50Z",
  "published": "2026-11-03T12:31:50Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99256"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0c7a8cad7c96012a9157a189649e569d0390f384"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/104f09e02038b0fc6bbb718b3976af029e15c1d0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2f2cfa16dd0f4179bb988139dd37d00a42324f6c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6290507ecc0dd6dd40759729cbbbd49b1d2a63c4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/73df2ff409f3db95029982fe3656329568e3715d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8433fd005c25fd127021f67c9144a879fb585572"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bc9781c0247de107876f32929f1637db93a42b34"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f5db935d257023c3ef410bd39163b949b0e5a55d"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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