[IPV6]: Fix tunnel list locking in ip6_tunnel.c

We need to fix tunnel list locking in ip6_tunnel.c as well.
Noticed by jean-mickael guerin <jean-mickael.guerin@6WIND.com>.
Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_tunnel.c

@@ -180,10 +180,10 @@ ip6ip6_tnl_link(struct ip6_tnl *t)
 {
 	struct ip6_tnl **tp = ip6ip6_bucket(&t->parms);
 
-	write_lock_bh(&ip6ip6_lock);
 	t->next = *tp;
-	write_unlock_bh(&ip6ip6_lock);
+	write_lock_bh(&ip6ip6_lock);
 	*tp = t;
+	write_unlock_bh(&ip6ip6_lock);
 }
 
 /**