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

Without this length argument, we can read past the end of the iovec in
memcpy_toiovec because we have no way of knowing the total length of the
iovec's buffers.

This is needed for stable kernels where 89c22d8c3b27 ("net: Fix skb
csum races when peeking") has been backported but that don't have the
ioviter conversion, which is almost all the stable trees <= 3.18.

This also fixes a kernel crash for NFS servers when the client uses
 -onfsvers=3,proto=udp to mount the export.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
[ luis: backported to 3.16:
  - dropped changes to net/rxrpc/ar-recvmsg.c ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

5 files changed, 10 insertions, 5 deletions

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 3c69a464595e..169f742d1464 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -818,6 +818,7 @@ 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.
  *
@@ -827,11 +828,14 @@ 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 hlen, struct iovec *iov, int len)
 {
 	__wsum csum;
 	int chunk = skb->len - hlen;
 
+	if (chunk > len)
+		chunk = len;
+
 	if (!chunk)
 		return 0;
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 486f70050563..0cdaa633059b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4906,7 +4906,7 @@ 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);
+						       tp->ucopy.iov, chunk);
 
 	if (!err) {
 		tp->ucopy.len -= chunk;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 10c1530ba978..4b9e4aba11b0 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1307,7 +1307,7 @@ try_again:
 	else {
 		err = skb_copy_and_csum_datagram_iovec(skb,
 						       sizeof(struct udphdr),
-						       msg->msg_iov);
+						       msg->msg_iov, copied);
 
 		if (err == -EINVAL)
 			goto csum_copy_err;
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index b2dc60b0c764..fd377c4d8986 100644
--- a/net/ipv6/raw.c
+++ b/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);
+		err = skb_copy_and_csum_datagram_iovec(skb, 0, msg->msg_iov, copied);
 		if (err == -EINVAL)
 			goto csum_copy_err;
 	}
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index ad5891072a89..72603a9af4bc 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -428,7 +428,8 @@ try_again:
 		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);
+		err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr),
+						       msg->msg_iov, copied);
 		if (err == -EINVAL)
 			goto csum_copy_err;
 	}