CVE-2026-90278md: wait for behind writes before destroying bitmap

Official description

In the Linux kernel, the following vulnerability has been resolved: md: wait for behind writes before destroying bitmap __md_stop() destroyed the bitmap before calling mddev_detach(). That made mddev_detach() skip bitmap_ops->wait_behind_writes(), because the bitmap was already disconnected from mddev. This was still safe for the legacy bitmap because bitmap_destroy() waits for behind writes itself. llbitmap keeps that wait in its ->wait_behind_writes() operation instead, while ->destroy() tears down the llbitmap storage. With the old ordering, RAID1 behind-write completions could still run after llbitmap storage had been freed. Call mddev_detach() before md_bitmap_destroy() so the common detach path can wait for behind writes while the bitmap is still alive. Only destroy the bitmap after those users are gone.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/73881ff7a75913f919a1ce9d9571bfaab8e8588d
• https://git.kernel.org/stable/c/4224dccd325a9380e8edfb66aad8bb5771c94222
• https://git.kernel.org/stable/c/2a79365b2278f16e163e4024086105693b421601