The Linux kernel contains a concurrency flaw in the Btrfs filesystem's defragmentation routine. The defragmenter reserves space in the delalloc area while holding dirty and locked folios and the extent range lock. When another kernel thread attempts to reserve delalloc space, a deadlock occurs. This can halt the kernel, leading to a system freeze or kernel panic.

The flaw affects all Linux kernel versions that ship the Btrfs file system before the patch that fixes the deadlock. No exact affected version range is listed, so any kernel lacking the commit identified in the references may be vulnerable. The issue is relevant to all distributions that use the upstream Linux kernel and include Btrfs support.

With an EPSS score below 1% and no presence in the CISA KEV catalog, the likelihood of public exploitation appears low. Exploitation would require the target to invoke Btrfs defragmentation or use utilities such as fsstress with autodefrag and flushoncommit enabled. Attackers would need local or elevated privileges to trigger the deadlock, and the effect is a denial‑of‑service rather than remote code execution.