CVE-2026-97446: ACPICA: Fix NULL pointer dereference in acpi_ns_custom_package()

CVE-2026-97446: ACPICA: Fix NULL pointer dereference in acpi_ns_custom_package()

[Greg Kroah-Hartman]

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

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

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

ACPICA: Fix NULL pointer dereference in acpi_ns_custom_package()

acpi_ns_custom_package() unconditionally dereferences the first element
of the package to read the _BIX version number, without checking for
NULL:

    if ((*Elements)->Common.Type != ACPI_TYPE_INTEGER)

When firmware returns a _BIX package whose first element is an
unresolvable reference, ACPICA evaluates that entry to NULL.
acpi_ns_remove_null_elements() does not strip NULL entries for
ACPI_PTYPE_CUSTOM packages (fixed-position format would break if
elements were shifted), so acpi_ns_custom_package() sees the NULL
and causes a crash.

Add a NULL check for the first element (version field) before
dereferencing it. The caller then receives AE_AML_OPERAND_TYPE
instead of crashing.

The Linux kernel CVE team has assigned CVE-2026-97446 to this issue.


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

	Fixed in 6.12.111 with commit 3762c6c8ae5073892d7cec736cc54270c7c9ce90
	Fixed in 6.18.53 with commit 3cbf096a478f4fa03953f0685ad28c9c82ce67cb
	Fixed in 7.2 with commit f8d14b7bb0063bbbd86c0e4d73edb8cea7b362bc

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-2026-97446
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:
	drivers/acpi/acpica/nsprepkg.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/3762c6c8ae5073892d7cec736cc54270c7c9ce90
	https://git.kernel.org/stable/c/3cbf096a478f4fa03953f0685ad28c9c82ce67cb
	https://git.kernel.org/stable/c/f8d14b7bb0063bbbd86c0e4d73edb8cea7b362bc