CVE-2026-90209

In the Linux kernel, the following vulnerability has been resolved:

s390/debug: Fix deadlock during unregister

Unregistering an s390dbf debug area while one of the associated debugfs

files is being written to can cause a deadlock:

$ echo >.../vmur/level $ rmmod vmur

===================================================

debugfs write

debugfs_file_get()

debug_unregister()

mutex_lock(debug_mutex)

debugfs_remove()

wait for debugfs_file_put()

debug_file_ops.write()

debug_input()

mutex_lock(debug_mutex) ==> DEADLOCK

Fix this by splitting debug_unregister() into an s390dbf and debugfs

part, and running only the s390dbf part with debug_mutex locked.