Subject: CVE-2024-44954: ALSA: line6: Fix racy access to midibuf

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

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

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

ALSA: line6: Fix racy access to midibuf

There can be concurrent accesses to line6 midibuf from both the URB
completion callback and the rawmidi API access.  This could be a cause
of KMSAN warning triggered by syzkaller below (so put as reported-by
here).

This patch protects the midibuf call of the former code path with a
spinlock for avoiding the possible races.

The Linux kernel CVE team has assigned CVE-2024-44954 to this issue.

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

	Fixed in 4.19.320 with commit 643293b68fbb
	Fixed in 5.4.282 with commit 40f3d5cb0e0c
	Fixed in 5.10.224 with commit e7e7d2b180d8
	Fixed in 5.15.165 with commit a54da4b787dc
	Fixed in 6.1.105 with commit c80f454a8054
	Fixed in 6.6.46 with commit 535df7f896a5
	Fixed in 6.10.5 with commit 51d87f11dd19
	Fixed in 6.11 with commit 15b7a03205b3

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-2024-44954
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/line6/driver.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/643293b68fbb6c03f5e907736498da17d43f0d81
	https://git.kernel.org/stable/c/40f3d5cb0e0cbf7fa697913a27d5d361373bdcf5
	https://git.kernel.org/stable/c/e7e7d2b180d8f297cea6db43ea72402fd33e1a29
	https://git.kernel.org/stable/c/a54da4b787dcac60b598da69c9c0072812b8282d
	https://git.kernel.org/stable/c/c80f454a805443c274394b1db0d1ebf477abd94e
	https://git.kernel.org/stable/c/535df7f896a568a8a1564114eaea49d002cb1747
	https://git.kernel.org/stable/c/51d87f11dd199bbc6a85982b088ff27bde53b48a
	https://git.kernel.org/stable/c/15b7a03205b31bc5623378c190d22b7ff60026f1