md/md-llbitmap: stop daemon timer rearm on destroy

Summary

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.

Timeline

1. Sep 17, 2026, 4:08 PM UTCCVE published
2. Oct 19, 2026, 9:00 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 5ab829f1971dc99f2aac10846c378e67fc875abc · fixed in c55aa6c17f019b6296952d336939891efa084c06; From 5ab829f1971dc99f2aac10846c378e67fc875abc · fixed in bb7f92d58fca9a9f06f3f51a82481c5f0bbbd46c; From 5ab829f1971dc99f2aac10846c378e67fc875abc · fixed in 5553d64e01d9a995be6c3de38501c6dd4ceede3b

• Linux Linux

  6.18

• KernelLinux

  From 6.18.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 3