packet: avoid out of bounds read in round robin fanout
authorWillem de Bruijn <willemb@google.com>
Wed, 17 Jun 2015 19:59:34 +0000 (15:59 -0400)
committerDavid S. Miller <davem@davemloft.net>
Sun, 21 Jun 2015 17:24:37 +0000 (10:24 -0700)
commit468479e6043c84f5a65299cc07cb08a22a28c2b1
tree09c287dc76541605f72e2f56cb61317906b56b6a
parent51f458d9612177f69c2e2c437034ae15f93078e7
packet: avoid out of bounds read in round robin fanout

PACKET_FANOUT_LB computes f->rr_cur such that it is modulo
f->num_members. It returns the old value unconditionally, but
f->num_members may have changed since the last store. Ensure
that the return value is always < num.

When modifying the logic, simplify it further by replacing the loop
with an unconditional atomic increment.

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