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]

kernel.org https://git.kernel.org/stable/c/03358aba991668d3bb2c65b3c82aa32c36851170 [No types assigned]

kernel.org https://git.kernel.org/stable/c/26dfe112ec2e95fe0099681f6aec33da13c2dd8e [No types assigned]

kernel.org https://git.kernel.org/stable/c/559b6322f9480bff68cfa98d108991e945a4f284 [No types assigned]

kernel.org https://git.kernel.org/stable/c/6cdedc18ba7b9dacc36466e27e3267d201948c8d [No types assigned]

kernel.org https://git.kernel.org/stable/c/aedda066d717a0b4335d7e0a00b2e3a61e40afcf [No types assigned]