netdev - Re: net: GPF in eth

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Message-ID: <1480362459.18162.83.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 28 Nov 2016 11:47:39 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        David Miller <davem@...emloft.net>,
        Tom Herbert <tom@...bertland.com>,
        Alexander Duyck <aduyck@...antis.com>,
        Jiri Benc <jbenc@...hat.com>,
        Sabrina Dubroca <sd@...asysnail.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: net: GPF in eth_header

On Mon, 2016-11-28 at 20:34 +0100, Dmitry Vyukov wrote:
> On Mon, Nov 28, 2016 at 8:04 PM, 'Andrey Konovalov' via syzkaller

> > Hi Eric,
> >
> > As far as I can see, skb_network_offset() becomes negative after
> > pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data) in nf_ct_frag6_queue().
> > At least I'm able to detect that with a BUG_ON().
> >
> > Also it seems that the issue is only reproducible (at least with the
> > poc I provided) for a short time after boot.
> 
> 
> Eric,
> 
> Is it enough to debug? Or maybe Andrey can trace some values for you.

Well, now we are talking, if you tell me how many modules you load, it
might help ;)

nf_ct_frag6_queue is nowhere to be seen in my kernels, that might
explain why I could not reproduce the bug.

Let me try ;)