Linux Kernel Zone Write Plug Deadlock Vulnerability

A potential deadlock vulnerability has been identified in the Linux kernel's handling of zoned block device writes. The issue arises during the error recovery process for zone write plugging, which is designed to manage writes to specific zones by ensuring the correct tracking of write pointers. When a write operation fails, the system schedules a zone report to correct the tracking. However, if a device queue freeze is initiated while write operations are still plugged and one fails, the reporting process can block, leading to a deadlock. This occurs because the plugged write operations hold a reference that prevents the queue freeze from completing, causing a standstill in processing the plugged writes.

Impact

Exploitation of this vulnerability leads to a deadlock, where the system becomes unresponsive due to conflicting operations that cannot be resolved.

Remediation

The vulnerability has been addressed by removing the automatic error recovery from the zone write plugging code. Users are now required to manually execute zone report, reset, finish, or disk revalidation operations after a write failure, which is a common practice for file systems that revert to read-only after encountering write errors.