From: Zhang Changzhong <zhangchangzhong@huawei.com>
To: Robin van der Gracht <robin@protonic.nl>,
Oleksij Rempel <linux@rempel-privat.de>, <kernel@pengutronix.de>,
Oliver Hartkopp <socketcan@hartkopp.net>,
Marc Kleine-Budde <mkl@pengutronix.de>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Maxime Jayat <maxime.jayat@mobile-devices.fr>,
<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
Date: Fri, 8 Oct 2021 17:22:12 +0800 [thread overview]
Message-ID: <1cab07f2-593a-1d1c-3a29-43ee9df4b29e@huawei.com> (raw)
In-Reply-To: <20210930074206.GB7502@x1.vandijck-laurijssen.be>
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 <zhangchangzhong@huawei.com>
>> ---
>> 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
>>
> .
>
next prev parent reply other threads:[~2021-10-08 9:22 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-30 3:33 [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length Zhang Changzhong
2021-09-30 7:42 ` Kurt Van Dijck
2021-10-08 9:22 ` Zhang Changzhong [this message]
2021-10-08 11:00 ` Oleksij Rempel
2021-10-08 17:09 ` Kurt Van Dijck
2021-10-09 9:12 ` Zhang Changzhong
2021-10-09 8:43 ` Zhang Changzhong
2021-10-11 6:35 ` Oleksij Rempel
2021-10-11 7:18 ` Kurt Van Dijck
2021-10-11 10:40 ` Zhang Changzhong
2021-10-12 10:21 ` Oleksij Rempel
2021-10-12 10:41 ` Kurt Van Dijck
2021-10-12 11:09 ` Oleksij Rempel
2021-10-17 10:32 ` Marc Kleine-Budde
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