From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C41D8C433EF for ; Wed, 20 Jul 2022 19:14:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230196AbiGTTO0 (ORCPT ); Wed, 20 Jul 2022 15:14:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229579AbiGTTOX (ORCPT ); Wed, 20 Jul 2022 15:14:23 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD7BC5720B for ; Wed, 20 Jul 2022 12:14:22 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1oEF90-0004W8-0J; Wed, 20 Jul 2022 21:14:02 +0200 Received: from ore by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1oEF8v-0005MV-H8; Wed, 20 Jul 2022 21:13:57 +0200 Date: Wed, 20 Jul 2022 21:13:57 +0200 From: Oleksij Rempel To: Fedor Pchelkin Cc: Robin van der Gracht , Oleksij Rempel , Pengutronix Kernel Team , Oliver Hartkopp , Marc Kleine-Budde , "David S. Miller" , Jakub Kicinski , Elenita Hinds , Kurt Van Dijck , linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Alexey Khoroshilov Subject: Re: [PATCH] can: j1939: Remove unnecessary WARN_ON_ONCE in j1939_sk_queue_activate_next_locked() Message-ID: <20220720191357.GB5600@pengutronix.de> References: <20220720110645.519601-1-pchelkin@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220720110645.519601-1-pchelkin@ispras.ru> 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: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Fedor, On Wed, Jul 20, 2022 at 02:06:45PM +0300, Fedor Pchelkin wrote: > The purpose of WARN_ON_ONCE if the session with the same parameters > has already been activated and is currently in active_session_list is > not very clear. Is this warning implemented to indicate that userspace > is doing something wrong? yes. > As far as I can see, there are two lists: active_session_list (which > is for the whole device) and sk_session_queue (which is unique for > each j1939_sock), and the situation when we have two sessions with > the same type, addresses and destinations in two different > sk_session_queues (owned by two different sockets) is actually highly > probable - one is active and the other is willing to become active > but the j1939_session_activate() does not let that happen. It is > correct behaviour as I assume. No. It is not typical use case and most probably it will create problems. Are you working on some system where this use case is valid? > Found by Linux Verification Center (linuxtesting.org) with Syzkaller. > > Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > Signed-off-by: Fedor Pchelkin > Signed-off-by: Alexey Khoroshilov > > --- > net/can/j1939/socket.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c > index f5ecfdcf57b2..be4b73afa16c 100644 > --- a/net/can/j1939/socket.c > +++ b/net/can/j1939/socket.c > @@ -178,7 +178,7 @@ static void j1939_sk_queue_activate_next_locked(struct j1939_session *session) > if (!first) > return; > > - if (WARN_ON_ONCE(j1939_session_activate(first))) { > + if (j1939_session_activate(first)) { > first->err = -EBUSY; > goto activate_next; > } else { > -- > 2.25.1 > > -- 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 |