Linux Kernel DM Cache background_work locking bug (rwsemaphore misuse)
CVE-2026-99256 Published on November 3, 2026
dm cache: fix issue with background work locking
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.
Products Associated with CVE-2026-99256
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Affected Versions
Linux:- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below 0c7a8cad7c96012a9157a189649e569d0390f384 is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below f5db935d257023c3ef410bd39163b949b0e5a55d is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4 is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below 8433fd005c25fd127021f67c9144a879fb585572 is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below 2f2cfa16dd0f4179bb988139dd37d00a42324f6c is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below 73df2ff409f3db95029982fe3656329568e3715d is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below 104f09e02038b0fc6bbb718b3976af029e15c1d0 is affected.
- Version b29d4986d0da1a27cd35917cdb433672f5c95d7f and below bc9781c0247de107876f32929f1637db93a42b34 is affected.
- Version 4.12 is affected.
- Before 4.12 is unaffected.
- Version 5.10.273, <= 5.10.* is unaffected.
- Version 5.15.224, <= 5.15.* is unaffected.
- Version 6.1.191, <= 6.1.* is unaffected.
- Version 6.6.161, <= 6.6.* is unaffected.
- Version 6.12.115, <= 6.12.* is unaffected.
- Version 6.18.59, <= 6.18.* is unaffected.
- Version 7.2.13, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.