Subject: CVE-2021-47091: mac80211: fix locking in ieee80211_start_ap error path

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

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

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

mac80211: fix locking in ieee80211_start_ap error path

We need to hold the local->mtx to release the channel context,
as even encoded by the lockdep_assert_held() there. Fix it.

The Linux kernel CVE team has assigned CVE-2021-47091 to this issue.

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

	Issue introduced in 5.10 with commit 295b02c4be74 and fixed in 5.10.89 with commit ac61b9c6c054
	Issue introduced in 5.10 with commit 295b02c4be74 and fixed in 5.15.12 with commit c1d1ec4db5f7
	Issue introduced in 5.10 with commit 295b02c4be74 and fixed in 5.16 with commit 87a270625a89

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-2021-47091
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:
	net/mac80211/cfg.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/ac61b9c6c0549aaeb98194cf429d93c41bfe5f79
	https://git.kernel.org/stable/c/c1d1ec4db5f7264cfc21993e59e8f2dcecf4b44f
	https://git.kernel.org/stable/c/87a270625a89fc841f1a7e21aae6176543d8385c