In the Linux kernel, a defect in the RAID5 subsystem causes an infinite loop when a write is performed on a degraded array that still relies on a logical bitmap (llbitmap). The bug arises because a check that should force a read‑back‑write on an unwritten bitmap location is omitted in the need_this_block() routine, even though it exists in handle_stripe_dirtying(). When a write reaches handle_stripe(), it decides to go to handle_stripe_fill(), but need_this_block() continuously returns 0, blocking the operation and leading to a deadloop. The result is an I/O stall that effectively hangs the array and denies all pending and future I/O operations.

Systems running Linux kernel versions that have not incorporated the upstream commits identified by 28ef299e7a5b81817f8ca8297c2ddff28f5da5e8, 870b9f15867b0e70f3459ef3974b043e8b229690, or cd1635d844d26471c56c0a432abdee12fc9ad735 are affected. The issue targets deployments that use RAID5 with the llbitmap feature, typically in enterprise storage or data‑center environments. Newer kernels that include these patches are not impacted.

The CVSS score has not been published and the EPSS score is unavailable, indicating no publicly available exploit data. The vulnerability is listed as not in the CISA KEV catalog. Exploitation requires the ability to issue writes to a degraded RAID5 array, which is normally a privilege of local users with write access. An attacker who can trigger such writes could cause prolonged I/O hangs, temporarily rendering the system unresponsive until a reboot or hardware reset.