netdev - Re: net/packet: use-after-free in packet_rcv

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Date:   Fri, 17 Feb 2017 11:27:15 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Sowmini Varadhan <sowmini.varadhan@...cle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Anoob Soman <anoob.soman@...rix.com>,
        David Miller <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>, jarno@....org,
        Philip Pettersson <philip.pettersson@...il.com>,
        weongyo.linux@...il.com, netdev <netdev@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/packet: use-after-free in packet_rcv_fanout

On Mon, Feb 13, 2017 at 7:17 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> Another similar one:
>

The other possibility is:  __fanout_link() is called twice on the same
packet sock
for some reason, but __fanout_unlink() only unlinks the first one, which led to
this use-after-free. However, the po->running and po->fanout seem enough
to guarantee this should not happen. I still want to point this out in case I
miss anything here so that other people could figure it out.