Re: net/packet: use-after-free in packet_rcv_fanout

[Eric Dumazet]

On Thu, Feb 9, 2017 at 7:12 AM, Sowmini Varadhan
<sowmini.varadhan@xxxxxxxxxx> wrote:
> 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?

RCU protection for hooks.