Subject: CVE-2023-52904: ALSA: usb-audio: Fix possible NULL pointer dereference in snd_usb_pcm_has_fixed_rate()

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

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

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

ALSA: usb-audio: Fix possible NULL pointer dereference in snd_usb_pcm_has_fixed_rate()

The subs function argument may be NULL, so do not use it before the NULL check.

The Linux kernel CVE team has assigned CVE-2023-52904 to this issue.

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

	Issue introduced in 5.15.152 with commit bfd36b1d1869 and fixed in 5.15.168 with commit f57204edc107

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-2023-52904
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/pcm.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/f57204edc10760c935d8d36ea999dc8acf018030
	https://git.kernel.org/stable/c/a474d4ad59cd4642d1b7e3a6c08cef9eca0992c8
	https://git.kernel.org/stable/c/92a9c0ad86d47ff4cce899012e355c400f02cfb8