Message-ID: <1480362459.18162.83.camel@edumazet-glaptop3.roam.corp.google.com>
Subject: Re: net: GPF in eth_header
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>,
        Hannes Frederic Sowa <hannes@stressinduktion.org>,
        David Miller <davem@davemloft.net>, Tom Herbert <tom@herbertland.com>,
        Alexander Duyck <aduyck@mirantis.com>, Jiri Benc <jbenc@redhat.com>,
        Sabrina Dubroca <sd@queasysnail.net>, netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Date: Mon, 28 Nov 2016 11:47:39 -0800
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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 ;)