[PATCH 4.9 04/59] inet: fix IP(V6)_RECVORIGDSTADDR for udp sockets

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Willem de Bruijn <willemb@xxxxxxxxxx>


[ Upstream commit 39b2dd765e0711e1efd1d1df089473a8dd93ad48 ]

Socket cmsg IP(V6)_RECVORIGDSTADDR checks that port range lies within
the packet. For sockets that have transport headers pulled, transport
offset can be negative. Use signed comparison to avoid overflow.

Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")
Reported-by: Nisar Jagabar <njagabar@xxxxxxxxxxxxx>
Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/ip_sockglue.c |    2 +-
 net/ipv6/datagram.c    |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -137,7 +137,7 @@ static void ip_cmsg_recv_dstaddr(struct
 	const struct iphdr *iph = ip_hdr(skb);
 	__be16 *ports = (__be16 *)skb_transport_header(skb);
 
-	if (skb_transport_offset(skb) + 4 > skb->len)
+	if (skb_transport_offset(skb) + 4 > (int)skb->len)
 		return;
 
 	/* All current transport protocols have the port numbers in the
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -700,7 +700,7 @@ void ip6_datagram_recv_specific_ctl(stru
 		struct sockaddr_in6 sin6;
 		__be16 *ports = (__be16 *) skb_transport_header(skb);
 
-		if (skb_transport_offset(skb) + 4 <= skb->len) {
+		if (skb_transport_offset(skb) + 4 <= (int)skb->len) {
 			/* All current transport protocols have the port numbers in the
 			 * first four bytes of the transport header and this function is
 			 * written with this assumption in mind.