# Re: \[PATCH net 3/3\] can: j1939: j1939\_tp\_cmd\_recv(): check the dst address of TP.CM\_BAM

- From: Zhang Changzhong \<hidden\>
- Date: 2021-10-25 06:59:43 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/10/1552093
- Thread: https://ratatoskr.run/linux-can/2021/10/1549639/t.md

```text
On 2021/10/22 18:28, Oleksij Rempel wrote:
> On Thu, Oct 21, 2021 at 10:04:17PM +0800, Zhang Changzhong wrote:
>> The TP.CM_BAM message must be sent to the global address [1], so add a
>> check to drop TP.CM_BAM sent to a non-global address.
>>
>> Without this patch, the receiver will treat the following packets as
>> normal RTS/CTS tranport:
>> 18EC0102#20090002FF002301
>> 18EB0102#0100000000000000
>> 18EB0102#020000FFFFFFFFFF
>>
>> [1] SAE-J1939-82 2015 A.3.3 Row 1.
>>
>> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
>> Signed-off-by: Zhang Changzhong <redacted>
>> ---
>>  net/can/j1939/transport.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
>> index 2efa606..93ec0c3 100644
>> --- a/net/can/j1939/transport.c
>> +++ b/net/can/j1939/transport.c
>> @@ -2019,6 +2019,8 @@ static void j1939_tp_cmd_recv(struct j1939_priv *priv, struct sk_buff *skb)
>>  		extd = J1939_ETP;
>>  		fallthrough;
>>  	case J1939_TP_CMD_BAM:
>> +		if (!j1939_cb_is_broadcast(skcb))
> 
> Please add here netdev_err_once("with some message"), we need to know if
> some MCU makes bad things.

Ok, will do.

The current patch breaks ETP functionality as the J1939_ETP_CMD_RTS fallthrough
to J1939_TP_CMD_BAM, this will also be fixed in v2.

> 
>> +			return;
>>  		fallthrough;
>>  	case J1939_TP_CMD_RTS:
>>  		if (skcb->addr.type != extd)
>> -- 
>> 2.9.5
>>
>>
> 
```