UBUNTU-CVE-2026-90401: High severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: md: remove REQNOWAIT support from raid1/10/456 REQNOWAIT support in md personalities that can block internally is fundamentally incomplete. While reads can avoid some blocking paths, write requests can still encounter cases where one mirror succeeds while another returns -EAGAIN. At that point md cannot distinguish queue pressure from a real device failure, so it can neither record a bad block nor safely retry the write without REQNOWAIT, leaving mirrors with divergent data. Rather than continue advertising REQNOWAIT support for personalities that cannot implement it correctly, remove it from raid1, raid10 and raid456. Keep REQNOWAIT for linear and raid0, which only remap bios to their underlying devices; stacked limits will still clear the feature if any component device lacks REQNOWAIT support.