tree d7938c4f52b72eb98d9e0d5c229c805547a277f8
parent 1579f678fb4397f9e439d2e373d4ade036c673b4
author Willem de Bruijn <willemb@google.com> 1506442777 -0400
committer David S. Miller <davem@davemloft.net> 1506619471 -0700

packet: in packet_do_bind, test fanout with bind_lock held

Once a socket has po->fanout set, it remains a member of the group
until it is destroyed. The prot_hook must be constant and identical
across sockets in the group.

If fanout_add races with packet_do_bind between the test of po->fanout
and taking the lock, the bind call may make type or dev inconsistent
with that of the fanout group.

Hold po->bind_lock when testing po->fanout to avoid this race.

I had to introduce artificial delay (local_bh_enable) to actually
observe the race.

Fixes: dc99f600698d ("packet: Add fanout support.")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>