Subject: CVE-2023-52638: can: j1939: prevent deadlock by changing j1939_socks_lock to rwlock

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

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

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

can: j1939: prevent deadlock by changing j1939_socks_lock to rwlock

The following 3 locks would race against each other, causing the
deadlock situation in the Syzbot bug report:

- j1939_socks_lock
- active_session_list_lock
- sk_session_queue_lock

A reasonable fix is to change j1939_socks_lock to an rwlock, since in
the rare situations where a write lock is required for the linked list
that j1939_socks_lock is protecting, the code does not attempt to
acquire any more locks. This would break the circular lock dependency,
where, for example, the current thread already locks j1939_socks_lock
and attempts to acquire sk_session_queue_lock, and at the same time,
another thread attempts to acquire j1939_socks_lock while holding
sk_session_queue_lock.

NOTE: This patch along does not fix the unregister_netdevice bug
reported by Syzbot; instead, it solves a deadlock situation to prepare
for one or more further patches to actually fix the Syzbot bug, which
appears to be a reference counting problem within the j1939 codebase.

[mkl: remove unrelated newline change]

The Linux kernel CVE team has assigned CVE-2023-52638 to this issue.

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

	Fixed in 5.15.149 with commit 03358aba9916
	Fixed in 6.1.79 with commit aedda066d717
	Fixed in 6.6.18 with commit 26dfe112ec2e
	Fixed in 6.7.6 with commit 559b6322f948
	Fixed in 6.8 with commit 6cdedc18ba7b

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-2023-52638
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/can/j1939/j1939-priv.h
	net/can/j1939/main.c
	net/can/j1939/socket.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/03358aba991668d3bb2c65b3c82aa32c36851170
	https://git.kernel.org/stable/c/aedda066d717a0b4335d7e0a00b2e3a61e40afcf
	https://git.kernel.org/stable/c/26dfe112ec2e95fe0099681f6aec33da13c2dd8e
	https://git.kernel.org/stable/c/559b6322f9480bff68cfa98d108991e945a4f284
	https://git.kernel.org/stable/c/6cdedc18ba7b9dacc36466e27e3267d201948c8d