The Linux kernel's md subsystem had a vulnerability involving the REQ_NOWAIT feature in raid1, raid10, and raid456 personalities. REQ_NOWAIT support was fundamentally incomplete because write requests could still block or return -EAGAIN errors, causing md to be unable to distinguish between queue pressure and device failure. This ambiguity prevented marking bad blocks or safely retrying writes, potentially leading to divergent data across mirrors. The resolution involved removing REQ_NOWAIT support from these RAID personalities, while keeping it for linear and raid0, which only remap bios and do not block internally.

This vulnerability could cause data integrity issues in RAID1, RAID10, and RAID456 configurations by allowing mirrors to have divergent data due to incomplete handling of write retries under REQ_NOWAIT. The inability to detect and handle device failures or queue pressure correctly could lead to data corruption or loss in affected RAID setups. There is no indication of confidentiality impact, but integrity and availability are affected.

A fix has been implemented that removes REQ_NOWAIT support from the affected RAID personalities (raid1, raid10, raid456) in the Linux kernel. Users should update to a kernel version that includes this fix to prevent data divergence issues. Since this is a kernel-level fix, upgrading the Linux kernel to a patched version is the recommended remediation.