Executive brief
A spurious warning is triggered in the Linux kernel's UDF filesystem when an I/O error occurs while writing the Logical Volume Integrity Descriptor buffer to disk. The warning is raised on subsequent filesystem remount or sync operations, even though the in-memory buffer data is valid. While this does not cause data loss or system compromise, the warning clutters system logs and can trigger automated alerting systems configured to react to kernel warnings.
Technical details
The vulnerability is a spurious kernel warning (WARN_ON_ONCE) in the UDF filesystem code. When an I/O error occurs while writing the Logical Volume Integrity Descriptor (LVID) buffer, the block layer clears the BH_Uptodate flag. On subsequent filesystem remount or sync, the kernel attempts to modify and re-mark the buffer dirty via mark_buffer_dirty(), which triggers a warning check for buffer_uptodate() even though the in-memory contents are valid. The fix sets the BH_Uptodate flag unconditionally before calling mark_buffer_dirty() in udf_open_lvid() and udf_sync_fs(). This requires local filesystem access and a prior I/O error condition, and the impact is limited to log spam and potential alerting noise rather than security compromise.
Affected products
- Linux Linux kernel various versions prior to the fix
Timeline
- 2026-09-17: disclosed