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

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

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

s390/debug: Fix NULL pointer dereference in debug_set_level()

Commit a2cec6863709 ("s390/debug: Add s390dbf kernel parameter")
incorrectly removed a null-id check from debug_set_level(), introducing
a possible NULL pointer dereference for debug-API users that put
debug_register() results unchecked into debug_set_level().

Fix this by moving the check from the internal _debug_set_level()
variant back to the external debug_set_level() wrapper.

The Linux kernel CVE team has assigned CVE-2026-97980 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 7.2 with commit a2cec6863709d6673a025acc066c962b85a75842 and fixed in 7.2.7 with commit 716e1cd3783806929407dbd596e6b1118971eb9e
	Issue introduced in 7.2 with commit a2cec6863709d6673a025acc066c962b85a75842 and fixed in 7.3-rc3 with commit b1eb31d533cdfcae1011ed53850d52f36afe5774

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-97980
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/s390/kernel/debug.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/716e1cd3783806929407dbd596e6b1118971eb9e
	https://git.kernel.org/stable/c/b1eb31d533cdfcae1011ed53850d52f36afe5774