CVE-2026-90209 PUBLISHED

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:

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.

• https://git.kernel.org/stable/c/a214c3dacc779b2afcb0ac9c8001e45ee4ffb2ed
• https://git.kernel.org/stable/c/183f8f6d64bb0510070c856b9927618c53014a7b
• https://git.kernel.org/stable/c/a08b70ed2d1ec907353a72f15163b8e34ff4b2f8
• https://git.kernel.org/stable/c/45bb341d1b73eb293e0dd43d9b72bbc8b615d0ba
• https://git.kernel.org/stable/c/5d83f3faa3fb7f23f298cfd40382611999de5d1d
• https://git.kernel.org/stable/c/54e1259b75d6402a1d0cfb822b9bb2c507e53dab
• https://git.kernel.org/stable/c/445c31ac638fd1af203d79bdf25fc0cb3149fbbc