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Subject: Re: v4.14-rc3/arm64 DABT exception in atomic_inc() / __skb_clone()
To: Eric Dumazet <edumazet@google.com>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: Wei Wei <dotweiba@gmail.com>, 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>,
        David Miller <davem@davemloft.net>,
        Willem de Bruijn <willemb@google.com>,
        syzkaller <syzkaller@googlegroups.com>
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From: Jason Wang <jasowang@redhat.com>
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Date: Thu, 26 Oct 2017 13:38:59 +0800
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On 2017年10月26日 03:01, Eric Dumazet wrote:
> On Wed, Oct 25, 2017 at 11:49 AM, Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
>
>>  From skb->dev and netdev_priv, the tun device has flags 0x1002 ==
>> IFF_TAP | IFF_NO_PI. This kernel precedes the recent support for
>> IFF_NAPI and IFF_NAPI_FRAGS. The allocation most likely happened
>> in tun_build_skb from current->task_frag. It would be a previous
>> allocation that left alloc_frag->offset unaligned. But perhaps this code
>> needs to perform alignment before setting skb->head. At least on
>> platforms where atomic on dataref must be aligned.
> +1
>
> Bug added in commit 66ccbc9c87c2 ("tap: use build_skb() for small packet")

Thanks, will post a patch.