Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <002d234f-a7d6-7b1a-72f4-157d7a283446@hartkopp.net>
Date:   Wed, 11 May 2022 16:50:06 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.1
Subject: Re: [PATCH 1/1] can: skb: add and set local_origin flag
Content-Language: en-US
To:     Marc Kleine-Budde <mkl@pengutronix.de>
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>
References: <20220511121913.2696181-1-o.rempel@pengutronix.de>
 <b631b022-72d5-9160-fd13-f33c80dbbe59@hartkopp.net>
 <20220511132421.7o5a3po32l3w2wcr@pengutronix.de>
 <20220511143620.kphwgp2vhjyoecs5@pengutronix.de>
From:   Oliver Hartkopp <socketcan@hartkopp.net>
In-Reply-To: <20220511143620.kphwgp2vhjyoecs5@pengutronix.de>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


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
>