Subject: CVE-2024-35842: ASoC: mediatek: sof-common: Add NULL check for normal_link string

From: Greg Kroah-Hartman <[email-masked]>

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

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

ASoC: mediatek: sof-common: Add NULL check for normal_link string

It's not granted that all entries of struct sof_conn_stream declare
a `normal_link` (a non-SOF, direct link) string, and this is the case
for SoCs that support only SOF paths (hence do not support both direct
and SOF usecases).

For example, in the case of MT8188 there is no normal_link string in
any of the sof_conn_stream entries and there will be more drivers
doing that in the future.

To avoid possible NULL pointer KPs, add a NULL check for `normal_link`.

The Linux kernel CVE team has assigned CVE-2024-35842 to this issue.

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

	Issue introduced in 6.0 with commit 0caf1120c583 and fixed in 6.1.75 with commit cad471227a37
	Issue introduced in 6.0 with commit 0caf1120c583 and fixed in 6.6.14 with commit b1d3db6740d0
	Issue introduced in 6.0 with commit 0caf1120c583 and fixed in 6.7.2 with commit cde6ca5872bf
	Issue introduced in 6.0 with commit 0caf1120c583 and fixed in 6.8 with commit e3b3ec967a7d

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-2024-35842
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:
	sound/soc/mediatek/common/mtk-dsp-sof-common.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/cad471227a37c0c7c080bfc9ed01b53750e82afe
	https://git.kernel.org/stable/c/b1d3db6740d0997ffc6e5a0d96ef7cbd62b35fdd
	https://git.kernel.org/stable/c/cde6ca5872bf67744dffa875a7cb521ab007b7ef
	https://git.kernel.org/stable/c/e3b3ec967a7d93b9010a5af9a2394c8b5c8f31ed