CVE-2026-90265: btrfs: defrag: fix deadlock between defrag and delalloc space reservation
btrfs: defrag: fix deadlock between defrag and delalloc space reservation
Affected Software
Event History
Frequently Asked Questions
Which systems are exposed to this deadlock?
Systems using the Linux kernel with Btrfs filesystems are relevant. The reported trigger involves Btrfs autodefrag and flushoncommit during filesystem stress activity.
What conditions are needed to trigger the issue?
The deadlock occurs when defragmentation reserves delayed-allocation space while holding dirty and locked folios and an extent-range lock. The report observed this while running fsstress with autodefrag and flushoncommit enabled.
What is the likely operational impact?
Affected tasks can enter an uninterruptible sleep state while Btrfs metadata-space reclaim and transaction processing wait on each other. This can stall filesystem-related work rather than providing an attacker with direct code execution.
What can be done if the kernel fix cannot be deployed immediately?
The provided data identifies autodefrag and flushoncommit as part of the observed trigger conditions. Avoiding that combination and avoiding defragmentation-heavy stress workloads may reduce exposure until an updated kernel containing one of the referenced stable commits is installed.