From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [IPv6:2a0a:edc0:2:b01:1d::104]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF90FA8 for ; Fri, 17 Nov 2023 00:10:26 -0800 (PST) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1r3tvT-0005ZF-4D; Fri, 17 Nov 2023 09:10:07 +0100 Received: from [2a0a:edc0:2:b01:1d::c0] (helo=ptx.whiteo.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1r3tvO-009d5q-RY; Fri, 17 Nov 2023 09:10:02 +0100 Received: from ore by ptx.whiteo.stw.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1r3tvO-002Tie-O0; Fri, 17 Nov 2023 09:10:02 +0100 Date: Fri, 17 Nov 2023 09:10:02 +0100 From: Oleksij Rempel To: Ziqi Zhao Cc: ivan.orlov0322@gmail.com, edumazet@google.com, syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com, socketcan@hartkopp.net, bridge@lists.linux-foundation.org, nikolay@nvidia.com, syzbot+1591462f226d9cbf0564@syzkaller.appspotmail.com, roopa@nvidia.com, kuba@kernel.org, pabeni@redhat.com, arnd@arndb.de, syzkaller-bugs@googlegroups.com, mudongliangabcd@gmail.com, linux-can@vger.kernel.org, mkl@pengutronix.de, skhan@linuxfoundation.org, robin@protonic.nl, linux-kernel@vger.kernel.org, linux@rempel-privat.de, kernel@pengutronix.de, netdev@vger.kernel.org, davem@davemloft.net Subject: Re: [PATCH] can: j1939: prevent deadlock by changing j1939_socks_lock to rwlock Message-ID: <20231117081002.GA590719@pengutronix.de> References: <20230704064710.3189-1-astrajoan@yahoo.com> <20230721162226.8639-1-astrajoan@yahoo.com> <20230807044634.GA5736@pengutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230807044634.GA5736@pengutronix.de> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-Accept-Language: de,en X-Accept-Content-Type: text/plain User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org 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@syzkaller.appspotmail.com > > Signed-off-by: Ziqi Zhao Reviewed-by: Oleksij Rempel -- 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 |