CVE-2026-99256 (GCVE-0-2026-99256)

Vulnerability from cvelistv5 – Published: 2026-11-03 11:25 – Updated: 2026-11-03 11:40
VLAI
Title
dm cache: fix issue with background work locking
Summary
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 <cache>, run: 'dmsetup suspend <cache> && dmsetup resume <cache>'. 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.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < 0c7a8cad7c96012a9157a189649e569d0390f384 (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < f5db935d257023c3ef410bd39163b949b0e5a55d (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4 (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < 8433fd005c25fd127021f67c9144a879fb585572 (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < 2f2cfa16dd0f4179bb988139dd37d00a42324f6c (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < 73df2ff409f3db95029982fe3656329568e3715d (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < 104f09e02038b0fc6bbb718b3976af029e15c1d0 (git)
Affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f , < bc9781c0247de107876f32929f1637db93a42b34 (git)
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Linux Linux Affected: 4.12
Unaffected: 0 , < 4.12 (semver)
Unaffected: 5.10.273 , ≤ 5.10.* (semver)
Unaffected: 5.15.224 , ≤ 5.15.* (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.161 , ≤ 6.6.* (semver)
Unaffected: 6.12.115 , ≤ 6.12.* (semver)
Unaffected: 6.18.59 , ≤ 6.18.* (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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          "value": "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."
        }
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    "datePublished": "2026-11-03T11:25:14.077Z",
    "dateReserved": "2026-09-25T10:25:14.404Z",
    "dateUpdated": "2026-11-03T11:40:45.109Z",
    "state": "PUBLISHED"
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            "value": "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."
          }
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        "id": "CVE-2026-99256",
        "lastModified": "2026-11-03T12:17:32.437",
        "metrics": {},
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-05T02:47:57+00:00",
      "cve": "CVE-2026-99256",
      "id": "CVE-2026-99256",
      "initial_release_date": "2026-11-03T11:25:14.077000+00:00",
      "product_status:known_affected": "204",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kernel: Denial of Service via improper lock ownership handling in dm-cache",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99256.json",
      "version": "3"
    }
  }
}



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