net: better drop monitoring in ip{6}_recv_error()

We should call consume_skb(skb) when skb is properly consumed,
or kfree_skb(skb) when skb must be dropped in error case.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -510,9 +510,10 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 		copied = len;
 	}
 	err = skb_copy_datagram_msg(skb, 0, msg, copied);
-	if (err)
-		goto out_free_skb;
-
+	if (unlikely(err)) {
+		kfree_skb(skb);
+		return err;
+	}
 	sock_recv_timestamp(msg, sk, skb);
 
 	serr = SKB_EXT_ERR(skb);
@@ -544,8 +545,7 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 	msg->msg_flags |= MSG_ERRQUEUE;
 	err = copied;
 
-out_free_skb:
-	kfree_skb(skb);
+	consume_skb(skb);
 out:
 	return err;
 }

net/ipv6/datagram.c

@@ -450,9 +450,10 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 		copied = len;
 	}
 	err = skb_copy_datagram_msg(skb, 0, msg, copied);
-	if (err)
-		goto out_free_skb;
-
+	if (unlikely(err)) {
+		kfree_skb(skb);
+		return err;
+	}
 	sock_recv_timestamp(msg, sk, skb);
 
 	serr = SKB_EXT_ERR(skb);
@@ -509,8 +510,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 	msg->msg_flags |= MSG_ERRQUEUE;
 	err = copied;
 
-out_free_skb:
-	kfree_skb(skb);
+	consume_skb(skb);
 out:
 	return err;
 }