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 ;-)
Best,
Oliver
> /* If the interface is not capable to do loopback
> * itself, we do it here.
> */
>
> Marc
>
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
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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
Hi Marc,
On 11.05.22 16:57, Oliver Hartkopp wrote:
>
>
> 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:
I double checked that code and when I didn't miss anything all the
callers of can_send() (e.g. raw_sendmsg()) are creating valid skbs.
https://elixir.bootlin.com/linux/v5.17.6/A/ident/can_send
>>>>
>>>> | 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;
>>>> +
That would make this change unnecessary, right?
IIRC the reason for can_dropped_invalid_skb() is to prove valid skbs for
CAN interface drivers when CAN frame skbs are created e.g. with
PF_PACKET sockets.
Best,
Oliver
>>>
>>> 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
>
On 12.05.2022 08:23:26, Oliver Hartkopp wrote:
> > > > > 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:
> I double checked that code and when I didn't miss anything all the callers
> of can_send() (e.g. raw_sendmsg()) are creating valid skbs.
ACK - I haven't checked, but I assume that all current callers of
can_send() are sound, this I why I started the description with: "Assume
an invalid CAN frame is passed to can_send()". But we can argue that we
trust all callers.
regards,
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |