CVE-2026-99256
dm cache: fix issue with background work locking
What happened?
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.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| LinuxLinux | affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < 0c7a8cad7c96012a9157a189649e569d0390f384; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < f5db935d257023c3ef410bd39163b949b0e5a55d; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < 6290507ecc0dd6dd40759729cbbbd49b1d2a63c4; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < 8433fd005c25fd127021f67c9144a879fb585572; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < 2f2cfa16dd0f4179bb988139dd37d00a42324f6c; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < 73df2ff409f3db95029982fe3656329568e3715d; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < 104f09e02038b0fc6bbb718b3976af029e15c1d0; affected: b29d4986d0da1a27cd35917cdb433672f5c95d7f to < bc9781c0247de107876f32929f1637db93a42b34 | See vendor advisory |
| LinuxLinux | affected: 4.12; unaffected: 0 to < 4.12; unaffected: 5.10.273 to ≤ 5.10.*; unaffected: 5.15.224 to ≤ 5.15.*; unaffected: 6.1.191 to ≤ 6.1.*; unaffected: 6.6.161 to ≤ 6.6.*; unaffected: 6.12.115 to ≤ 6.12.*; unaffected: 6.18.59 to ≤ 6.18.*; unaffected: 7.2.13 to ≤ 7.2.*; unaffected: 7.3 to ≤ * | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.
Sources and remediation references
- https://www.cve.org/CVERecord?id=CVE-2026-99256
- https://git.kernel.org/stable/c/0c7a8cad7c96012a9157a189649e569d0390f384
- https://git.kernel.org/stable/c/f5db935d257023c3ef410bd39163b949b0e5a55d
- https://git.kernel.org/stable/c/6290507ecc0dd6dd40759729cbbbd49b1d2a63c4
- https://git.kernel.org/stable/c/8433fd005c25fd127021f67c9144a879fb585572
- https://git.kernel.org/stable/c/2f2cfa16dd0f4179bb988139dd37d00a42324f6c
- https://git.kernel.org/stable/c/73df2ff409f3db95029982fe3656329568e3715d
- https://git.kernel.org/stable/c/104f09e02038b0fc6bbb718b3976af029e15c1d0
- https://git.kernel.org/stable/c/bc9781c0247de107876f32929f1637db93a42b34