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CVE-2026-99256: In the Linux kernel, the following vulnerability has been resolved: dm cache: fix issue with background work locking dm…
- Source
- NVD(opens in a new tab)
- Identifier
- CVE-2026-99256
- Published
- Record updated
- Known exploitation
- Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.
Summary
CVE-2026-99256 affects the Linux kernel's dm cache device-mapper target. The background_work_lock was a rw_semaphore, but write locks on it have strict owner semantics, and nothing guaranteed that the process unlocking it was the one that locked it. Running 'dmsetup suspend <cache> && dmsetup resume <cache>' on a kernel built with CONFIG_DEBUG_RWSEMS triggers a kernel warning from cache_resume().
Mitigation
The fix replaces the rw_semaphore with a spinlock and a wait queue. The existing migration_wait queue and nr_allocated_migrations counter are repurposed as the background_work queue and counter.