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 9E4F4C4332F for ; Sat, 9 Oct 2021 08:44:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 80DD660F23 for ; Sat, 9 Oct 2021 08:44:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231700AbhJIIp6 (ORCPT ); Sat, 9 Oct 2021 04:45:58 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:25113 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230479AbhJIIp5 (ORCPT ); Sat, 9 Oct 2021 04:45:57 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4HRJTY3v3kz1DHTJ; Sat, 9 Oct 2021 16:42:25 +0800 (CST) Received: from dggpeml500006.china.huawei.com (7.185.36.76) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Sat, 9 Oct 2021 16:43:57 +0800 Received: from [10.174.178.240] (10.174.178.240) by dggpeml500006.china.huawei.com (7.185.36.76) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Sat, 9 Oct 2021 16:43:56 +0800 From: Zhang Changzhong Subject: Re: [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length To: Oleksij Rempel CC: Robin van der Gracht , Oleksij Rempel , , Oliver Hartkopp , Marc Kleine-Budde , "David S. Miller" , Jakub Kicinski , Maxime Jayat , , , References: <1632972800-45091-1-git-send-email-zhangchangzhong@huawei.com> <20210930074206.GB7502@x1.vandijck-laurijssen.be> <1cab07f2-593a-1d1c-3a29-43ee9df4b29e@huawei.com> <20211008110007.GE29653@pengutronix.de> Message-ID: <556a04ed-c350-7b2b-5bbe-98c03846630b@huawei.com> Date: Sat, 9 Oct 2021 16:43:56 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20211008110007.GE29653@pengutronix.de> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.240] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500006.china.huawei.com (7.185.36.76) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/10/8 19:00, Oleksij Rempel wrote: > 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"? Yes. Regards, Changzhong > > Regards, > Oleksij >