{"id":"CVE-2026-99256","title":"dm cache: fix issue with background work locking","summary":"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 t…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 0c7a8cad7c96012a9157a189649e569d0390f384","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < f5db935d257023c3ef410bd39163b949b0e5a55d","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 8433fd005c25fd127021f67c9144a879fb585572","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 2f2cfa16dd0f4179bb988139dd37d00a42324f6c","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 73df2ff409f3db95029982fe3656329568e3715d","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 104f09e02038b0fc6bbb718b3976af029e15c1d0","Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < bc9781c0247de107876f32929f1637db93a42b34","Linux 4.12"],"published":"2026-11-03","updated":"2026-11-03","sourceUpdated":"2026-11-03T11:40:45.109Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99256","references":[{"url":"https://git.kernel.org/stable/c/0c7a8cad7c96012a9157a189649e569d0390f384"},{"url":"https://git.kernel.org/stable/c/f5db935d257023c3ef410bd39163b949b0e5a55d"},{"url":"https://git.kernel.org/stable/c/6290507ecc0dd6dd40759729cbbbd49b1d2a63c4"},{"url":"https://git.kernel.org/stable/c/8433fd005c25fd127021f67c9144a879fb585572"},{"url":"https://git.kernel.org/stable/c/2f2cfa16dd0f4179bb988139dd37d00a42324f6c"},{"url":"https://git.kernel.org/stable/c/73df2ff409f3db95029982fe3656329568e3715d"},{"url":"https://git.kernel.org/stable/c/104f09e02038b0fc6bbb718b3976af029e15c1d0"},{"url":"https://git.kernel.org/stable/c/bc9781c0247de107876f32929f1637db93a42b34"}],"tags":["cve.org"],"epss":0.00202,"epssPercentile":0.10155,"ingestedAt":"2026-11-05T19:30:42.939Z","slug":"CVE-2026-99256","body":"## Overview\n\nIn 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 <cache>, run: 'dmsetup\nsuspend <cache> && dmsetup resume <cache>'. This will trigger a kernel\nwarning:\n\nDEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !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't\nactually used by anything. This is replaced by the background_work queue\nand counter.\n\n## Affected\n\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 0c7a8cad7c96012a9157a189649e569d0390f384`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < f5db935d257023c3ef410bd39163b949b0e5a55d`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 8433fd005c25fd127021f67c9144a879fb585572`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 2f2cfa16dd0f4179bb988139dd37d00a42324f6c`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 73df2ff409f3db95029982fe3656329568e3715d`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < 104f09e02038b0fc6bbb718b3976af029e15c1d0`\n- `Linux >= b29d4986d0da1a27cd35917cdb433672f5c95d7f < bc9781c0247de107876f32929f1637db93a42b34`\n- `Linux 4.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}