udp: prevent skbs lingering in tunnel socket queues

[ Upstream commit e5aed006 ]

In case we find a socket with encapsulation enabled we should call
the encap_recv function even if just a udp header without payload is
available. The callbacks are responsible for correctly verifying and
dropping the packets.

Also, in case the header validation fails for geneve and vxlan we
shouldn't put the skb back into the socket queue, no one will pick
them up there.  Instead we can simply discard them in the respective
encap_recv functions.
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16:
 - Drop changes to geneve
 - vxlan error checking looked a bit different]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/vxlan.c

@@ -1146,7 +1146,7 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 
 	/* Need Vxlan and inner Ethernet header to be present */
 	if (!pskb_may_pull(skb, VXLAN_HLEN))
-		goto error;
+		goto drop;
 
 	/* Return packets with reserved bits set */
 	vxh = (struct vxlanhdr *)(udp_hdr(skb) + 1);
@@ -1154,7 +1154,7 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	    (vxh->vx_vni & htonl(0xff))) {
 		netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
 			   ntohl(vxh->vx_flags), ntohl(vxh->vx_vni));
-		goto error;
+		goto drop;
 	}
 
 	if (iptunnel_pull_header(skb, VXLAN_HLEN, htons(ETH_P_TEB)))
@@ -1173,10 +1173,6 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	/* Consume bad packet */
 	kfree_skb(skb);
 	return 0;
-
-error:
-	/* Return non vxlan pkt */
-	return 1;
 }
 
 static void vxlan_rcv(struct vxlan_sock *vs,

net/ipv4/udp.c

@@ -1533,7 +1533,7 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 
 		/* if we're overly short, let UDP handle it */
 		encap_rcv = ACCESS_ONCE(up->encap_rcv);
-		if (skb->len > sizeof(struct udphdr) && encap_rcv != NULL) {
+		if (encap_rcv) {
 			int ret;
 
 			/* Verify checksum before giving to encap */

net/ipv6/udp.c

@@ -631,7 +631,7 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 
 		/* if we're overly short, let UDP handle it */
 		encap_rcv = ACCESS_ONCE(up->encap_rcv);
-		if (skb->len > sizeof(struct udphdr) && encap_rcv != NULL) {
+		if (encap_rcv) {
 			int ret;
 
 			/* Verify checksum before giving to encap */