On Mon, Aug 07, 2023 at 06:46:34AM +0200, Oleksij Rempel wrote: > On Fri, Jul 21, 2023 at 09:22:26AM -0700, Ziqi Zhao wrote: > > 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. > > > > Reported-by: syzbot+1591462f226d9cbf0564@xxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Ziqi Zhao <astrajoan@xxxxxxxxx> Reviewed-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
