CVE-2026-74642: ALSA: usb: Fix UAF at delayed release of MIDI2 EPs

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

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

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

ALSA: usb: Fix UAF at delayed release of MIDI2 EPs

The recent fix for UAF in ump_to_endpoint() caused another UAF because
it tries to dereference the UMP endpoint object, but this might be
executed at a delayed context where the endpoint has been already
released.

Add private_free to clear the associated data for avoiding the further
dereference for delayed releases.

The Linux kernel CVE team has assigned CVE-2026-74642 to this issue.


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

	Issue introduced in 6.6.151 with commit 49eccef6d6e1c00dac6fb2e7eb6f9206c33e1c37 and fixed in 6.6.152 with commit d431941825d357be7d9ab0cb7505e3a1963bd89e
	Issue introduced in 6.12.103 with commit 8a7a33b846d6ba695891b8d0040027cdbad8cd52 and fixed in 6.12.104 with commit 422d8a02de5ce6a29d616d55e5ead5dec69ac1d7
	Issue introduced in 6.18.44 with commit cc014ebf803174f0e5d15956dfc5a38413c945ae and fixed in 6.18.45 with commit d217d723c5e43881b952cdb978477f7f2dc0b6d7
	Issue introduced in 7.1.8 with commit ae388c0e1bf727972096f770f82d12e4f748d1b6 and fixed in 7.1.9 with commit f9d492a39ebeb1a56f13ec6dd165a18a48dec812

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-2026-74642
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/midi2.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/d431941825d357be7d9ab0cb7505e3a1963bd89e
	https://git.kernel.org/stable/c/422d8a02de5ce6a29d616d55e5ead5dec69ac1d7
	https://git.kernel.org/stable/c/d217d723c5e43881b952cdb978477f7f2dc0b6d7
	https://git.kernel.org/stable/c/f9d492a39ebeb1a56f13ec6dd165a18a48dec812
	https://git.kernel.org/stable/c/f8a80cfb68613fb7e6452b66447dbc63f435d140