bridge: fix RCU races with bridge port

The macro br_port_exists() is not enough protection when only
RCU is being used. There is a tiny race where other CPU has cleared port
handler hook, but is bridge port flag might still be set.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 3 deletions

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index b862071bf601..46e0bec1d7c5 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -151,11 +151,19 @@ struct net_bridge_port
 #endif
 };
 
-#define br_port_get_rcu(dev) \
-        ((struct net_bridge_port *) rcu_dereference(dev->rx_handler_data))
-#define br_port_get(dev) ((struct net_bridge_port *) dev->rx_handler_data)
 #define br_port_exists(dev) (dev->priv_flags & IFF_BRIDGE_PORT)
 
+static inline struct net_bridge_port *br_port_get_rcu(const struct net_device *dev)
+{
+        struct net_bridge_port *port = rcu_dereference(dev->rx_handler_data);
+        return br_port_exists(dev) ? port : NULL;
+}
+
+static inline struct net_bridge_port *br_port_get(struct net_device *dev)
+{
+        return br_port_exists(dev) ? dev->rx_handler_data : NULL;
+}
+
 struct br_cpu_netstats {
         u64                     rx_packets;
         u64                     rx_bytes;