Merge branch 'udp-hdrs-fixes'

Willem de Bruijn says:

====================
fix two more udp pull header issues

Follow up patches to the fixes to RxRPC and SunRPC. A scan of the
code showed two other interfaces that expect UDP packets to have
a udphdr when queued: read packet length with ioctl SIOCINQ and
receive payload checksum with socket option IP_CHECKSUM.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -106,7 +106,8 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
 		return;
 
 	if (offset != 0)
-		csum = csum_sub(csum, csum_partial(skb->data, offset, 0));
+		csum = csum_sub(csum, csum_partial(skb_transport_header(skb),
+						   offset, 0));
 
 	put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum);
 }

net/ipv4/udp.c

@@ -1282,8 +1282,6 @@ int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
 			 * of this packet since that is all
 			 * that will be read.
 			 */
-			amount -= sizeof(struct udphdr);
-
 		return put_user(amount, (int __user *)arg);
 	}
 
@@ -1377,7 +1375,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
-		ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr));
+		ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr) + off);
 
 	err = copied;
 	if (flags & MSG_TRUNC)