CVE-2026-90209: s390/debug: Fix deadlock during unregister

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-17 · updated 2026-10-19

Description

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.

Affected products

Linux kernel: from 5.4.146 before 5.5; from 5.10.65 before 5.11; from 5.13.17 before 5.14; from 5.14.4 before 5.15; 5.15 — fixed in 5.11, 5.14, 5.15, 5.5, 7.3

How to fix

Upgrade to a fixed version: Linux kernel 5.11, 5.14, 5.15, 5.5. Check the vendor advisory for mitigations.

References

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