CVE-2026-80816: ALSA: FCP: Use a private URB for the notification endpoint

CVE-2026-80816: ALSA: FCP: Use a private URB for the notification endpoint

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

ALSA: FCP: Use a private URB for the notification endpoint

fcp_init_notify() used mixer->urb, which snd_usb_mixer_status_create()
allocates for the optional UAC2 status interrupt endpoint and mixer.c
kills, resubmits and frees. On a device with that endpoint,
fcp_init_notify()'s "already set up" early return fires on the status
URB and returns success without doing anything. No FCP notification
URB is submitted, and cmd_done is left zeroed because it is
initialised past that early return and nowhere else. fcp_init() then
issues init1_opcode and wait_for_completion_timeout() would crash
adding to the zeroed wait.head. fcp_cleanup_urb() would also kill and
free mixer.c's status URB.

Use a separate URB in fcp_data, and initialise cmd_done in
fcp_init_private() where fcp_data is allocated. fcp_init_notify() is
reached again after suspend via fcp_reinit(), and the URB kill path in
fcp_notify() completes cmd_done, leaving a stale count that would
satisfy the next command's wait before the device ACKs. Use
reinit_completion() to clear it.

The Linux kernel CVE team has assigned CVE-2026-80816 to this issue.


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

	Issue introduced in 6.14 with commit 46757a3e7d50dac923888e7fbe68377736f13c70 and fixed in 6.18.47 with commit 65aceb45ca91ddb7f7ed178821f481b34da35543
	Issue introduced in 6.14 with commit 46757a3e7d50dac923888e7fbe68377736f13c70 and fixed in 7.1.11 with commit 5da21a434171e8ecf1d992c6f1d84c0c706fd395
	Issue introduced in 6.14 with commit 46757a3e7d50dac923888e7fbe68377736f13c70 and fixed in 7.2.1 with commit 6db3c1d7e2872c9904e05ca8e0515920776a3c9c
	Issue introduced in 6.14 with commit 46757a3e7d50dac923888e7fbe68377736f13c70 and fixed in 7.3-rc1 with commit 918b8d231c571c50a00efe92ffc8404a537a0490

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-2026-80816
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/fcp.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/65aceb45ca91ddb7f7ed178821f481b34da35543
	https://git.kernel.org/stable/c/5da21a434171e8ecf1d992c6f1d84c0c706fd395
	https://git.kernel.org/stable/c/6db3c1d7e2872c9904e05ca8e0515920776a3c9c
	https://git.kernel.org/stable/c/918b8d231c571c50a00efe92ffc8404a537a0490