bridge: fix NULL pointer deref of br_port_get_rcu
authorHong Zhiguo <zhiguohong@tencent.com>
Sat, 14 Sep 2013 14:42:28 +0000 (22:42 +0800)
committerDavid S. Miller <davem@davemloft.net>
Mon, 16 Sep 2013 02:03:33 +0000 (22:03 -0400)
commit716ec052d2280d511e10e90ad54a86f5b5d4dcc2
treed1746e5302a4bfcd86d1155e0f4882b0b8e07fa4
parent1fb1754a8c70d69ab480763c423e0a74369c4a67
bridge: fix NULL pointer deref of br_port_get_rcu

The NULL deref happens when br_handle_frame is called between these
2 lines of del_nbp:
dev->priv_flags &= ~IFF_BRIDGE_PORT;
/* --> br_handle_frame is called at this time */
netdev_rx_handler_unregister(dev);

In br_handle_frame the return of br_port_get_rcu(dev) is dereferenced
without check but br_port_get_rcu(dev) returns NULL if:
!(dev->priv_flags & IFF_BRIDGE_PORT)

Eric Dumazet pointed out the testing of IFF_BRIDGE_PORT is not necessary
here since we're in rcu_read_lock and we have synchronize_net() in
netdev_rx_handler_unregister. So remove the testing of IFF_BRIDGE_PORT
and by the previous patch, make sure br_port_get_rcu is called in
bridging code.

Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/bridge/br_private.h