---
id: CVE-2026-99256
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 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'
---

## Overview

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

- `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`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.