Linux Kernel Btrfs Scrub and Relocation Deadlock Vulnerability

A deadlock vulnerability has been identified in the Linux kernel's Btrfs file system, specifically during the block group relocation process when a scrub operation is also running. The issue arises because the relocation pauses the scrub, starts a transaction, and then attempts to unpause the scrub. If an error occurs during the transaction commit, the scrub cannot resume, leading to a deadlock. This vulnerability affects several versions of the Linux kernel, including 6.3.0-rc2.

Impact

Exploitation of this vulnerability causes a deadlock, where the scrub and relocation processes block each other, leading to prolonged system hangs.

Reproduction

The vulnerability can be reproduced by running a scrub operation on a Btrfs file system, then initiating a block group relocation. If an error occurs during the transaction commit of the relocation, the scrub will be left paused, causing both processes to hang indefinitely.

Remediation

Users can update to the latest version of the Linux kernel, where this vulnerability has been addressed.