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Date:   Wed, 11 May 2022 16:36:20 +0200
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Oliver Hartkopp <socketcan@hartkopp.net>
Cc:     Oleksij Rempel <o.rempel@pengutronix.de>,
        Wolfgang Grandegger <wg@grandegger.com>,
        Devid Antonio Filoni <devid.filoni@egluetechnologies.com>,
        kernel@pengutronix.de, linux-can@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        David Jander <david@protonic.nl>
Subject: Re: [PATCH 1/1] can: skb: add and set local_origin flag
Message-ID: <20220511143620.kphwgp2vhjyoecs5@pengutronix.de>
References: <20220511121913.2696181-1-o.rempel@pengutronix.de>
 <b631b022-72d5-9160-fd13-f33c80dbbe59@hartkopp.net>
 <20220511132421.7o5a3po32l3w2wcr@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.
> >=20
> > You probably need to revisit every place where can_skb_reserve() is use=
d,
> > e.g. in raw_sendmsg().
>=20
> And the loopback for devices that don't support IFF_ECHO:
>=20
> | 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 val=
id:

| 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)
                 */
=20
                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

--=20
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 |

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