Subject: CVE-2021-47211: ALSA: usb-audio: fix null pointer dereference on pointer cs_desc

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

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

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

ALSA: usb-audio: fix null pointer dereference on pointer cs_desc

The pointer cs_desc return from snd_usb_find_clock_source could
be null, so there is a potential null pointer dereference issue.
Fix this by adding a null check before dereference.

The Linux kernel CVE team has assigned CVE-2021-47211 to this issue.

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

	Fixed in 5.15.5 with commit 58fa50de595f
	Fixed in 5.16 with commit b97053df0f04

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-2021-47211
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/usb/clock.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/58fa50de595f152900594c28ec9915c169643739
	https://git.kernel.org/stable/c/b97053df0f04747c3c1e021ecbe99db675342954