Re: [PATCH net] can: j1939: j1939_xtp_rx_rts_session_new(): abort TP less than 9 bytes

[Oleksij Rempel]

On Thu, Oct 14, 2021 at 05:26:40PM +0800, Zhang Changzhong wrote:
> The receiver should abort TP if 'total message size' in TP.CM_RTS and
> TP.CM_BAM is less than 9 or greater than 1785 [1], but currently the
> j1939 stack only checks the upper bound and the receiver will accept the
> following broadcast message:
>   vcan1  18ECFF00   [8]  20 08 00 02 FF 00 23 01
>   vcan1  18EBFF00   [8]  01 00 00 00 00 00 00 00
>   vcan1  18EBFF00   [8]  02 00 FF FF FF FF FF FF
> 
> This patch adds check for the lower bound and abort illegal TP.
> 
> [1] SAE-J1939-82 A.3.4 Row 2 and A.3.6 Row 6.
> 
> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
> Signed-off-by: Zhang Changzhong <zhangchangzhong@xxxxxxxxxx>

Acked-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
Thank you!

> ---
>  net/can/j1939/j1939-priv.h | 1 +
>  net/can/j1939/transport.c  | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/net/can/j1939/j1939-priv.h b/net/can/j1939/j1939-priv.h
> index f6df208..16af1a7 100644
> --- a/net/can/j1939/j1939-priv.h
> +++ b/net/can/j1939/j1939-priv.h
> @@ -330,6 +330,7 @@ int j1939_session_activate(struct j1939_session *session);
>  void j1939_tp_schedule_txtimer(struct j1939_session *session, int msec);
>  void j1939_session_timers_cancel(struct j1939_session *session);
>  
> +#define J1939_MIN_TP_PACKET_SIZE 9
>  #define J1939_MAX_TP_PACKET_SIZE (7 * 0xff)
>  #define J1939_MAX_ETP_PACKET_SIZE (7 * 0x00ffffff)
>  
> diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
> index bb5c4b8..b685d31 100644
> --- a/net/can/j1939/transport.c
> +++ b/net/can/j1939/transport.c
> @@ -1609,6 +1609,8 @@ j1939_session *j1939_xtp_rx_rts_session_new(struct j1939_priv *priv,
>  			abort = J1939_XTP_ABORT_FAULT;
>  		else if (len > priv->tp_max_packet_size)
>  			abort = J1939_XTP_ABORT_RESOURCE;
> +		else if (len < J1939_MIN_TP_PACKET_SIZE)
> +			abort = J1939_XTP_ABORT_FAULT;
>  	}
>  
>  	if (abort != J1939_XTP_NO_ABORT) {
> -- 
> 2.9.5
> 
> 

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