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 A815BC433FE for ; Fri, 8 Oct 2021 09:22:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B00C60F58 for ; Fri, 8 Oct 2021 09:22:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237056AbhJHJYM (ORCPT ); Fri, 8 Oct 2021 05:24:12 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:13878 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229637AbhJHJYK (ORCPT ); Fri, 8 Oct 2021 05:24:10 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4HQjJR5b2dz90BM; Fri, 8 Oct 2021 17:17:27 +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; Fri, 8 Oct 2021 17:22:13 +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; Fri, 8 Oct 2021 17:22:12 +0800 Subject: Re: [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length To: 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> From: Zhang Changzhong Message-ID: <1cab07f2-593a-1d1c-3a29-43ee9df4b29e@huawei.com> Date: Fri, 8 Oct 2021 17:22:12 +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: <20210930074206.GB7502@x1.vandijck-laurijssen.be> 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: netdev@vger.kernel.org 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). Best regards, Changzhong > > Kind regards, > Kurt >> + } >> >> switch (session->last_cmd) { >> case 0xff: >> @@ -1904,7 +1907,7 @@ static void j1939_xtp_rx_dat_one(struct j1939_session *session, >> out_session_cancel: >> kfree_skb(se_skb); >> j1939_session_timers_cancel(session); >> - j1939_session_cancel(session, J1939_XTP_ABORT_FAULT); >> + j1939_session_cancel(session, abort); >> j1939_session_put(session); >> } >> >> -- >> 2.9.5 >> > . >