Revert "[stable-only] net: add length argument to skb_copy_and_csum_datagram_iovec"

This reverts commit fa89ae55.

As reported by Michal Kubecek, the backport of commit 89c22d8c
("net: Fix skb csum races when peeking") exposed an upstream bug.
It is being reverted and replaced by a better fix.
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

include/linux/skbuff.h

@@ -2525,7 +2525,7 @@ unsigned int datagram_poll(struct file *file, struct socket *sock,
 int skb_copy_datagram_iovec(const struct sk_buff *from, int offset,
 			    struct iovec *to, int size);
 int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb, int hlen,
-				     struct iovec *iov, int len);
+				     struct iovec *iov);
 int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
 				 const struct iovec *from, int from_offset,
 				 int len);

net/core/datagram.c

@@ -818,7 +818,6 @@ EXPORT_SYMBOL(__skb_checksum_complete);
  *	@skb: skbuff
  *	@hlen: hardware length
  *	@iov: io vector
- *	@len: amount of data to copy from skb to iov
  *
  *	Caller _must_ check that skb will fit to this iovec.
  *
@@ -828,14 +827,11 @@ EXPORT_SYMBOL(__skb_checksum_complete);
  *			   can be modified!
  */
 int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
-				     int hlen, struct iovec *iov, int len)
+				     int hlen, struct iovec *iov)
 {
 	__wsum csum;
 	int chunk = skb->len - hlen;
 
-	if (chunk > len)
-		chunk = len;
-
 	if (!chunk)
 		return 0;
 

net/ipv4/tcp_input.c

@@ -4903,7 +4903,7 @@ static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
 		err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
 	else
 		err = skb_copy_and_csum_datagram_iovec(skb, hlen,
-						       tp->ucopy.iov, chunk);
+						       tp->ucopy.iov);
 
 	if (!err) {
 		tp->ucopy.len -= chunk;

net/ipv4/udp.c

@@ -1307,7 +1307,7 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	else {
 		err = skb_copy_and_csum_datagram_iovec(skb,
 						       sizeof(struct udphdr),
-						       msg->msg_iov, copied);
+						       msg->msg_iov);
 
 		if (err == -EINVAL)
 			goto csum_copy_err;

net/ipv6/raw.c

@@ -492,7 +492,7 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 			goto csum_copy_err;
 		err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
 	} else {
-		err = skb_copy_and_csum_datagram_iovec(skb, 0, msg->msg_iov, copied);
+		err = skb_copy_and_csum_datagram_iovec(skb, 0, msg->msg_iov);
 		if (err == -EINVAL)
 			goto csum_copy_err;
 	}

net/ipv6/udp.c

@@ -428,8 +428,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
 					      msg->msg_iov, copied);
 	else {
-		err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr),
-						       msg->msg_iov, copied);
+		err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov);
 		if (err == -EINVAL)
 			goto csum_copy_err;
 	}