net: bridge: check the length of skb after nf_bridge_maybe_copy_header()

Since nf_bridge_maybe_copy_header() may change the length of skb,
we should check the length of skb after it to handle the ppoe skbs.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_forward.c

@@ -41,18 +41,14 @@ static inline unsigned packet_length(const struct sk_buff *skb)
 
 int br_dev_queue_push_xmit(struct sk_buff *skb)
 {
-	/* drop mtu oversized packets except gso */
-	if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
-		kfree_skb(skb);
-	else {
 	/* ip_fragment doesn't copy the MAC header */
-		if (nf_bridge_maybe_copy_header(skb))
+	if (nf_bridge_maybe_copy_header(skb) ||
+	    (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))) {
 		kfree_skb(skb);
-		else {
+	} else {
 		skb_push(skb, ETH_HLEN);
 		dev_queue_xmit(skb);
 	}
-	}
 
 	return 0;
 }