linux-kernel - Re: v4.14-rc3/arm64 DABT exception in atomic_inc() / __skb

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Message-ID: <7d13751a-5a7b-ff67-5f00-92e27861b24a@redhat.com>
Date:   Thu, 26 Oct 2017 13:38:59 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Wei Wei <dotweiba@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: v4.14-rc3/arm64 DABT exception in atomic_inc() / __skb_clone()



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@...il.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.