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

[Oliver Hartkopp]

On 5/11/22 16:54, Marc Kleine-Budde wrote:
> On 11.05.2022 16:50:06, Oliver Hartkopp wrote:
> > On 5/11/22 16:36, Marc Kleine-Budde wrote:
> > > 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;
> > > +
> >
> > Good point!
> >
> > But please check the rest of the code.
> > You need 'goto inval_skb;' instead of the return ;-)
>
> Why? To free the skb? That's what can_dropped_invalid_skb() does, too:
>
> | https://elixir.bootlin.com/linux/v5.17.6/source/include/linux/can/skb.h#L130

My bad!

Pointing you not reading the code ... should better have looked myself :-D