Subject: CVE-2021-47382: s390/qeth: fix deadlock during failing recovery

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

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

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

s390/qeth: fix deadlock during failing recovery

Commit 0b9902c1fcc5 ("s390/qeth: fix deadlock during recovery") removed
taking discipline_mutex inside qeth_do_reset(), fixing potential
deadlocks. An error path was missed though, that still takes
discipline_mutex and thus has the original deadlock potential.

Intermittent deadlocks were seen when a qeth channel path is configured
offline, causing a race between qeth_do_reset and ccwgroup_remove.
Call qeth_set_offline() directly in the qeth_do_reset() error case and
then a new variant of ccwgroup_set_offline(), without taking
discipline_mutex.

The Linux kernel CVE team has assigned CVE-2021-47382 to this issue.

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

	Issue introduced in 5.11 with commit b41b554c1ee7 and fixed in 5.14.10 with commit 0bfe74174132
	Issue introduced in 5.11 with commit b41b554c1ee7 and fixed in 5.15 with commit d2b59bd4b06d
	Issue introduced in 5.10.8 with commit af0c184ea106

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-2021-47382
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:
	arch/s390/include/asm/ccwgroup.h
	drivers/s390/cio/ccwgroup.c
	drivers/s390/net/qeth_core_main.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/0bfe741741327822d1482c7edef0184636d08b40
	https://git.kernel.org/stable/c/d2b59bd4b06d84a4eadb520b0f71c62fe8ec0a62