Linux Kernel RAID IO Flag Handling Vulnerability

A vulnerability in the Linux kernel's RAID1 and RAID10 implementations has been addressed. The issue arose because the RAID write performance was significantly degraded when block writeback throttling (blk-wbt) was enabled by default. This degradation occurred because all I/O operations were throttled by the writeback time (wbt) of the underlying disks, as the REQ_IDLE flag was ignored. This problem has persisted since the introduction of blk-wbt. Additionally, other I/O flags, such as REQ_META and REQ_NOWAIT, were improperly managed, leading to potential priority reversal issues and unnecessary I/O wait times. The vulnerability has been fixed by ensuring that I/O flags are correctly maintained from the master bio.

Impact

The vulnerability could lead to degraded RAID write performance, causing I/O operations to be improperly throttled and managed, which could disrupt normal data processing and storage operations.