Re: [PATCH 1/1] can: skb: add and set local_origin flag

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 11.05.2022 15:24:21, Marc Kleine-Budde wrote:
> On 11.05.2022 14:38:32, Oliver Hartkopp wrote:
> > IMO this patch does not work as intended.
> > 
> > You probably need to revisit every place where can_skb_reserve() is used,
> > e.g. in raw_sendmsg().
> 
> And the loopback for devices that don't support IFF_ECHO:
> 
> | https://elixir.bootlin.com/linux/latest/source/net/can/af_can.c#L257

BTW: There is a bug with interfaces that don't support IFF_ECHO.

Assume an invalid CAN frame is passed to can_send() on an interface that
doesn't support IFF_ECHO. The above mentioned code does happily generate
an echo frame and it's send, even if the driver drops it, due to
can_dropped_invalid_skb(dev, skb).

The echoed back CAN frame is treated in raw_rcv() as if the headroom is valid:

| https://elixir.bootlin.com/linux/v5.17.6/source/net/can/raw.c#L138

But as far as I can see the can_skb_headroom_valid() check never has
been done. What about this patch?

index 1fb49d51b25d..fda4807ad165 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -255,6 +255,9 @@ int can_send(struct sk_buff *skb, int loop)
                 */
 
                if (!(skb->dev->flags & IFF_ECHO)) {
+                       if (can_dropped_invalid_skb(dev, skb))
+                               return -EINVAL;
+
                        /* If the interface is not capable to do loopback
                         * itself, we do it here.
                         */

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
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