Revert "udp: remove redundant variable"

This reverts commit 81d54ec8.

If we take the "try_again" goto, due to a checksum error,
the 'len' has already been truncated.  So we won't compute
the same values as the original code did.
Reported-by: paul bilke <fsmail@conspiracy.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp.c

@@ -1164,7 +1164,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	struct inet_sock *inet = inet_sk(sk);
 	struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
 	struct sk_buff *skb;
-	unsigned int ulen;
+	unsigned int ulen, copied;
 	int peeked;
 	int err;
 	int is_udplite = IS_UDPLITE(sk);
@@ -1186,9 +1186,10 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 		goto out;
 
 	ulen = skb->len - sizeof(struct udphdr);
-	if (len > ulen)
-		len = ulen;
-	else if (len < ulen)
+	copied = len;
+	if (copied > ulen)
+		copied = ulen;
+	else if (copied < ulen)
 		msg->msg_flags |= MSG_TRUNC;
 
 	/*
@@ -1197,14 +1198,14 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	 * coverage checksum (UDP-Lite), do it before the copy.
 	 */
 
-	if (len < ulen || UDP_SKB_CB(skb)->partial_cov) {
+	if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) {
 		if (udp_lib_checksum_complete(skb))
 			goto csum_copy_err;
 	}
 
 	if (skb_csum_unnecessary(skb))
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
-					      msg->msg_iov, len);
+					      msg->msg_iov, copied);
 	else {
 		err = skb_copy_and_csum_datagram_iovec(skb,
 						       sizeof(struct udphdr),
@@ -1233,7 +1234,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	if (inet->cmsg_flags)
 		ip_cmsg_recv(msg, skb);
 
-	err = len;
+	err = copied;
 	if (flags & MSG_TRUNC)
 		err = ulen;
 

net/ipv6/udp.c

@@ -340,7 +340,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct inet_sock *inet = inet_sk(sk);
 	struct sk_buff *skb;
-	unsigned int ulen;
+	unsigned int ulen, copied;
 	int peeked;
 	int err;
 	int is_udplite = IS_UDPLITE(sk);
@@ -363,9 +363,10 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 		goto out;
 
 	ulen = skb->len - sizeof(struct udphdr);
-	if (len > ulen)
-		len = ulen;
-	else if (len < ulen)
+	copied = len;
+	if (copied > ulen)
+		copied = ulen;
+	else if (copied < ulen)
 		msg->msg_flags |= MSG_TRUNC;
 
 	is_udp4 = (skb->protocol == htons(ETH_P_IP));
@@ -376,14 +377,14 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 	 * coverage checksum (UDP-Lite), do it before the copy.
 	 */
 
-	if (len < ulen || UDP_SKB_CB(skb)->partial_cov) {
+	if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) {
 		if (udp_lib_checksum_complete(skb))
 			goto csum_copy_err;
 	}
 
 	if (skb_csum_unnecessary(skb))
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
-					      msg->msg_iov,len);
+					      msg->msg_iov, copied       );
 	else {
 		err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov);
 		if (err == -EINVAL)
@@ -432,7 +433,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 			datagram_recv_ctl(sk, msg, skb);
 	}
 
-	err = len;
+	err = copied;
 	if (flags & MSG_TRUNC)
 		err = ulen;