openvswitch: Fix race.

ovs_vport_cmd_dump() did rcu_read_lock() only after getting the
datapath, which could have been deleted in between.  Resolved by
taking rcu_read_lock() before the get_dp() call.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index e42340d3f820..8601b320b443 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1762,11 +1762,12 @@ static int ovs_vport_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
         int bucket = cb->args[0], skip = cb->args[1];
         int i, j = 0;
 
+        rcu_read_lock();
         dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
-        if (!dp)
+        if (!dp) {
+                rcu_read_unlock();
                 return -ENODEV;
-
-        rcu_read_lock();
+        }
         for (i = bucket; i < DP_VPORT_HASH_BUCKETS; i++) {
                 struct vport *vport;