netdev - Re: WARNING in can

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Message-ID: <CACT4Y+b0oUPVr7f973ZgBm9rUog=-mRWDFpcr-EzKaGYRnn8mQ@mail.gmail.com>
Date:   Tue, 16 Jan 2018 19:11:07 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     syzbot <syzbot+4386709c0c1284dca827@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>, linux-can@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        syzkaller-bugs@...glegroups.com
Subject: Re: WARNING in can_rcv

On Tue, Jan 16, 2018 at 7:07 PM, Marc Kleine-Budde <mkl@...gutronix.de> wrote:
> On 01/16/2018 06:58 PM, syzbot wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> a8750ddca918032d6349adbf9a4b6555e7db20da
>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>> C reproducer is attached
>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>> for information about syzkaller reproducers
>>
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+4386709c0c1284dca827@...kaller.appspotmail.com
>> It will help syzbot understand when the bug is fixed. See footer for
>> details.
>> If you forward the report, please keep this part and the footer.
>>
>> device eql entered promiscuous mode
>> ------------[ cut here ]------------
>> PF_CAN: dropped non conform CAN skbuf: dev type 65534, len 42, datalen 0
>> WARNING: CPU: 0 PID: 3650 at net/can/af_can.c:729 can_rcv+0x1c5/0x200
>> net/can/af_can.c:724
>> Kernel panic - not syncing: panic_on_warn set ...
>
> Invalid packages generate a warning (WARN_ONCE()), and you have
> panic_on_warn active. Should we better silently drop these CAN packages?

Hi,

pr_warn_once() will be more appropriate. It prints a single line.