From: Zhang Changzhong <zhangchangzhong@huawei.com>
To: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: 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: Sat, 9 Oct 2021 16:43:56 +0800 [thread overview]
Message-ID: <556a04ed-c350-7b2b-5bbe-98c03846630b@huawei.com> (raw)
In-Reply-To: <20211008110007.GE29653@pengutronix.de>
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 <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).
>
> 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
>
next prev parent reply other threads:[~2021-10-09 8:44 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
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 [this message]
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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