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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B76CDC433F5 for ; Fri, 8 Oct 2021 11:00:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A26F6101E for ; Fri, 8 Oct 2021 11:00:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239650AbhJHLCX (ORCPT ); Fri, 8 Oct 2021 07:02:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55642 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239911AbhJHLCW (ORCPT ); Fri, 8 Oct 2021 07:02:22 -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 737A1C061755 for ; Fri, 8 Oct 2021 04:00:27 -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 1mYnbl-0003cn-Hz; Fri, 08 Oct 2021 13:00:09 +0200 Received: from ore by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1mYnbj-0002EF-Ku; Fri, 08 Oct 2021 13:00:07 +0200 Date: Fri, 8 Oct 2021 13:00:07 +0200 From: Oleksij Rempel To: Zhang Changzhong Cc: Robin van der Gracht , Oleksij Rempel , kernel@pengutronix.de, Oliver Hartkopp , Marc Kleine-Budde , "David S. Miller" , Jakub Kicinski , Maxime Jayat , linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length Message-ID: <20211008110007.GE29653@pengutronix.de> References: <1632972800-45091-1-git-send-email-zhangchangzhong@huawei.com> <20210930074206.GB7502@x1.vandijck-laurijssen.be> <1cab07f2-593a-1d1c-3a29-43ee9df4b29e@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1cab07f2-593a-1d1c-3a29-43ee9df4b29e@huawei.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 12:47:01 up 232 days, 14:10, 145 users, load average: 0.04, 0.14, 0.16 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-can@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org On Fri, Oct 08, 2021 at 05:22:12PM +0800, Zhang Changzhong wrote: > Hi Kurt, > Sorry for the late reply. > > On 2021/9/30 15:42, Kurt Van Dijck wrote: > > On Thu, 30 Sep 2021 11:33:20 +0800, Zhang Changzhong wrote: > >> According to SAE-J1939-21, the data length of TP.DT must be 8 bytes, so > >> cancel session when receive unexpected TP.DT message. > > > > SAE-j1939-21 indeed says that all TP.DT must be 8 bytes. > > However, the last TP.DT may contain up to 6 stuff bytes, which have no meaning. > > If I remember well, they are even not 'reserved'. > > Agree, these bytes are meaningless for last TP.DT. > > > > >> > >> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > >> Signed-off-by: Zhang Changzhong > >> --- > >> net/can/j1939/transport.c | 7 +++++-- > >> 1 file changed, 5 insertions(+), 2 deletions(-) > >> > >> diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c > >> index bb5c4b8..eedaeaf 100644 > >> --- a/net/can/j1939/transport.c > >> +++ b/net/can/j1939/transport.c > >> @@ -1789,6 +1789,7 @@ static void j1939_xtp_rx_dpo(struct j1939_priv *priv, struct sk_buff *skb, > >> static void j1939_xtp_rx_dat_one(struct j1939_session *session, > >> struct sk_buff *skb) > >> { > >> + enum j1939_xtp_abort abort = J1939_XTP_ABORT_FAULT; > >> struct j1939_priv *priv = session->priv; > >> struct j1939_sk_buff_cb *skcb, *se_skcb; > >> struct sk_buff *se_skb = NULL; > >> @@ -1803,9 +1804,11 @@ static void j1939_xtp_rx_dat_one(struct j1939_session *session, > >> > >> skcb = j1939_skb_to_cb(skb); > >> dat = skb->data; > >> - if (skb->len <= 1) > >> + if (skb->len != 8) { > >> /* makes no sense */ > >> + abort = J1939_XTP_ABORT_UNEXPECTED_DATA; > >> goto out_session_cancel; > > > > I think this is a situation of > > "be strict on what you send, be tolerant on what you receive". > > > > Did you find a technical reason to abort a session because the last frame didn't > > bring overhead that you don't use? > > No technical reason. The only reason is that SAE-J1939-82 requires responder > to abort session if any TP.DT less than 8 bytes (section A.3.4, Row 7). Do you mean: "BAM Transport: Ensure DUT discards BAM transport when TP.DT data packets are not correct size" ... "Verify DUT discards the BAM transport if any TP.DT data packet has less than 8 bytes"? Regards, Oleksij -- 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 |