packet: hold bind lock when rebinding to fanout hook
authorWillem de Bruijn <willemb@google.com>
Thu, 14 Sep 2017 21:14:41 +0000 (17:14 -0400)
committerDavid S. Miller <davem@davemloft.net>
Wed, 20 Sep 2017 20:57:19 +0000 (13:57 -0700)
commit008ba2a13f2d04c947adc536d19debb8fe66f110
treee6d5a2faacf4925192f0197f6cf60c5640a1cfaa
parent35e015e1f5773417952fe91ce8790baf9b4237a2
packet: hold bind lock when rebinding to fanout hook

Packet socket bind operations must hold the po->bind_lock. This keeps
po->running consistent with whether the socket is actually on a ptype
list to receive packets.

fanout_add unbinds a socket and its packet_rcv/tpacket_rcv call, then
binds the fanout object to receive through packet_rcv_fanout.

Make it hold the po->bind_lock when testing po->running and rebinding.
Else, it can race with other rebind operations, such as that in
packet_set_ring from packet_rcv to tpacket_rcv. Concurrent updates
can result in a socket being added to a fanout group twice, causing
use-after-free KASAN bug reports, among others.

Reported independently by both trinity and syzkaller.
Verified that the syzkaller reproducer passes after this patch.

Fixes: dc99f600698d ("packet: Add fanout support.")
Reported-by: nixioaming <nixiaoming@huawei.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/packet/af_packet.c