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From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Wei Wei <dotweiba@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	LKML <linux-kernel@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	David Miller <davem@davemloft.net>,
	Willem de Bruijn <willemb@google.com>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: v4.14-rc3/arm64 DABT exception in atomic_inc() / __skb_clone()
Date: Wed, 25 Oct 2017 14:24:02 -0400	[thread overview]
Message-ID: <CAF=yD-JFjjA=2T7HermH2GygfHinyW+ZC5v+Di7M4V_Fg5paHg@mail.gmail.com> (raw)
In-Reply-To: <D2AD6D5B-3A05-48E7-A999-DECAB18A4649@gmail.com>

On Sat, Oct 21, 2017 at 9:56 PM, Wei Wei <dotweiba@gmail.com> wrote:
> I have uploaded the VM core dump [1]. And I don’t know if these logs are helpful in the case of
> failing to get the C reproducer currently.
>
> [1] https://github.com/dotweiba/skb_clone_atomic_inc_bug/blob/master/vmcore.gz

Thanks. So this would be the atomic_inc on shb_shinfo(skb)->dataref, which
matches the __ll_sc_atomic_add in Mark's trace.

Debugging with crash shows 0xffff800071bb3180 and 0xffff800071bb2c80
to be valid skbuffs of len 40, no sk, both pointing to the same head.

That is indeed unaligned:  head = 0xffff8000327c80c9 "", end = 256, giving
skb_shared_info at 0xffff8000327c81c9 and  &skb_shared_info(skb)->dataref
at 0xffff8000327c81c9 + 36 == 0xffff8000327c81ed

WARNING: multiple messages have this Message-ID (diff)
From: willemdebruijn.kernel@gmail.com (Willem de Bruijn)
To: linux-arm-kernel@lists.infradead.org
Subject: v4.14-rc3/arm64 DABT exception in atomic_inc() / __skb_clone()
Date: Wed, 25 Oct 2017 14:24:02 -0400	[thread overview]
Message-ID: <CAF=yD-JFjjA=2T7HermH2GygfHinyW+ZC5v+Di7M4V_Fg5paHg@mail.gmail.com> (raw)
In-Reply-To: <D2AD6D5B-3A05-48E7-A999-DECAB18A4649@gmail.com>

On Sat, Oct 21, 2017 at 9:56 PM, Wei Wei <dotweiba@gmail.com> wrote:
> I have uploaded the VM core dump [1]. And I don?t know if these logs are helpful in the case of
> failing to get the C reproducer currently.
>
> [1] https://github.com/dotweiba/skb_clone_atomic_inc_bug/blob/master/vmcore.gz

Thanks. So this would be the atomic_inc on shb_shinfo(skb)->dataref, which
matches the __ll_sc_atomic_add in Mark's trace.

Debugging with crash shows 0xffff800071bb3180 and 0xffff800071bb2c80
to be valid skbuffs of len 40, no sk, both pointing to the same head.

That is indeed unaligned:  head = 0xffff8000327c80c9 "", end = 256, giving
skb_shared_info at 0xffff8000327c81c9 and  &skb_shared_info(skb)->dataref
at 0xffff8000327c81c9 + 36 == 0xffff8000327c81ed

  reply	other threads:[~2017-10-25 18:24 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-20  2:16 v4.14-rc3/arm64 DABT exception in atomic_inc() / __skb_clone() Wei Wei
2017-10-20  2:16 ` Wei Wei
2017-10-20  2:53 ` Eric Dumazet
2017-10-20  2:53   ` Eric Dumazet
2017-10-20  3:13   ` Wei Wei
2017-10-20  3:13     ` Wei Wei
2017-10-20  5:34     ` Eric Dumazet
2017-10-20  5:34       ` Eric Dumazet
2017-10-20  9:18       ` Will Deacon
2017-10-20  9:18         ` Will Deacon
2017-10-20 11:14 ` Mark Rutland
2017-10-20 11:14   ` Mark Rutland
2017-10-20 14:40   ` Wei Wei
2017-10-20 14:40     ` Wei Wei
2017-10-20 15:11     ` Mark Rutland
2017-10-20 15:11       ` Mark Rutland
2017-10-20 15:14     ` Dmitry Vyukov
2017-10-20 15:14       ` Dmitry Vyukov
2017-10-20 15:39       ` Willem de Bruijn
2017-10-20 15:39         ` Willem de Bruijn
2017-10-22  1:56         ` Wei Wei
2017-10-22  1:56           ` Wei Wei
2017-10-25 18:24           ` Willem de Bruijn [this message]
2017-10-25 18:24             ` Willem de Bruijn
2017-10-25 18:49             ` Willem de Bruijn
2017-10-25 18:49               ` Willem de Bruijn
2017-10-25 19:01               ` Eric Dumazet
2017-10-25 19:01                 ` Eric Dumazet
2017-10-26  5:38                 ` Jason Wang
2017-10-26  5:38                   ` Jason Wang
2017-10-26 15:24               ` David Laight
2017-10-26 15:24                 ` David Laight
2017-10-26 15:24                 ` David Laight

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