linux-kernel - Re: net/packet: use-after-free in packet_rcv

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Date:   Thu, 9 Feb 2017 07:12:20 -0800
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     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@...il.com, weongyo.linux@...il.com,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net/packet: use-after-free in packet_rcv_fanout

On (02/09/17 14:14), Dmitry Vyukov wrote:
> 
> Call Trace:
   :
>  packet_rcv_has_room+0x25/0xb0 net/packet/af_packet.c:1308
>  fanout_demux_rollover+0x3bb/0x6b0 net/packet/af_packet.c:1388
>  packet_rcv_fanout+0x674/0x800 net/packet/af_packet.c:1490
>  dev_queue_xmit_nit+0x73a/0xa90 net/core/dev.c:1898
    :
>  tcp_sendmsg_fastopen net/ipv4/tcp.c:1110 [inline]
    :

looks like a race between a NIT socket (tcpdump, maybe?) that is closing,
and a standard tcp socket.. packet_release() takes the po->bind_lock
to remove the socket from the ptype_all NIT queue. but how does
that sync with the Tx path for other af_inet/af_inet6 sockets? 

--Sowmini