CVE-2026-90276
UnknownSummary
In the Linux kernel, the md/md-llbitmap subsystem's llbitmap_destroy() deletes pending_timer before flushing md_llbitmap_io_wq, but daemon_work can still be queued or running and rearm pending_timer. If this happens during teardown, the timer can remain armed after llbitmap is freed and later dereference freed memory. The fix adds a BITMAP_SHUTDOWN bit and uses timer_shutdown_sync().
Risk Assessment
Can lead to use-after-free and kernel crashes during llbitmap destruction. May result in system instability or data loss on md arrays.
Recommendation
Update the Linux kernel to a version containing the fix with the BITMAP_SHUTDOWN bit and timer_shutdown_sync(). Deploy the update before routinely removing arrays that use llbitmap.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: md/md-llbitmap: stop daemon timer rearm on destroy llbitmap_destroy() deletes pending_timer before flushing md_llbitmap_io_wq. However, daemon_work can still be queued or running after the timer has been deleted, and the daemon path can arm pending_timer again when it finds dirty chunks that are not ready to flush yet. If that happens during teardown, pending_timer can remain armed after llbitmap is freed and later dereference freed memory. Add a BITMAP_SHUTDOWN bit to llbitmap->flags, set it before deleting the timer, and make the timer and daemon paths stop queueing or rearming work once teardown starts. Cancel daemon_work before flushing the shared workqueue so no already queued daemon instance can race with the free. Use timer_shutdown_sync() so a daemon instance that passed the shutdown check before teardown cannot rearm the timer afterward. BITMAP_SHUTDOWN is a runtime-only state. Mask it out when reading and updating the llbitmap superblock so the shutdown state is never loaded from disk or persisted to disk.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS