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>
diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index 35cf270..3d9a55d 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -141,10 +141,6 @@
struct net_bridge *br;
const unsigned char *buf;
- if (!br_port_exists(dev))
- goto err;
- p = br_port_get_rcu(dev);
-
if (!pskb_may_pull(skb, 4))
goto err;
@@ -153,6 +149,10 @@
if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
goto err;
+ p = br_port_get_rcu(dev);
+ if (!p)
+ goto err;
+
br = p->br;
spin_lock(&br->lock);