CVE-2026-97980 s390/debug: Fix NULL pointer dereference in debug_set_level()

In the Linux kernel, the following vulnerability has been resolved: s390/debug: Fix NULL pointer dereference in debugsetlevel Commit a2cec6863709 "s390/debug: Add s390dbf kernel parameter" incorrectly removed a null-id check from debugsetlevel, introducing a possible NULL pointer dereference for...