dst: Clone child entry in skb_dst_pop

We clone the child entry in skb_dst_pop before we call
skb_dst_drop(). Otherwise we might kill the child right
before we return it to the caller.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dst.h

@@ -345,7 +345,7 @@ static inline void skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev)
 
 static inline struct dst_entry *skb_dst_pop(struct sk_buff *skb)
 {
-	struct dst_entry *child = skb_dst(skb)->child;
+	struct dst_entry *child = dst_clone(skb_dst(skb)->child);
 
 	skb_dst_drop(skb);
 	return child;

net/xfrm/xfrm_output.c

@@ -96,7 +96,7 @@ static int xfrm_output_one(struct sk_buff *skb, int err)
 			err = -EHOSTUNREACH;
 			goto error_nolock;
 		}
-		skb_dst_set(skb, dst_clone(dst));
+		skb_dst_set(skb, dst);
 		x = dst->xfrm;
 	} while (x && !(x->outer_mode->flags & XFRM_MODE_FLAG_TUNNEL));