net: Fix skb_under_panic oops in neigh_resolve_output

[ Upstream commit e1f16503 ]

The retry loop in neigh_resolve_output() and neigh_connected_output()
call dev_hard_header() with out reseting the skb to network_header.
This causes the retry to fail with skb_under_panic. The fix is to
reset the network_header within the retry loop.
Signed-off-by: Ramesh Nagappa <ramesh.nagappa@ericsson.com>
Reviewed-by: Shawn Lu <shawn.lu@ericsson.com>
Reviewed-by: Robert Coulson <robert.coulson@ericsson.com>
Reviewed-by: Billie Alsup <billie.alsup@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/core/neighbour.c

@@ -1313,8 +1313,6 @@ int neigh_resolve_output(struct sk_buff *skb)
 	if (!dst)
 		goto discard;
 
-	__skb_pull(skb, skb_network_offset(skb));
-
 	if (!neigh_event_send(neigh, skb)) {
 		int err;
 		struct net_device *dev = neigh->dev;
@@ -1326,6 +1324,7 @@ int neigh_resolve_output(struct sk_buff *skb)
 			neigh_hh_init(neigh, dst, dst->ops->protocol);
 
 		do {
+			__skb_pull(skb, skb_network_offset(skb));
 			seq = read_seqbegin(&neigh->ha_lock);
 			err = dev_hard_header(skb, dev, ntohs(skb->protocol),
 					      neigh->ha, NULL, skb->len);
@@ -1358,9 +1357,8 @@ int neigh_connected_output(struct sk_buff *skb)
 	struct net_device *dev = neigh->dev;
 	unsigned int seq;
 
-	__skb_pull(skb, skb_network_offset(skb));
-
 	do {
+		__skb_pull(skb, skb_network_offset(skb));
 		seq = read_seqbegin(&neigh->ha_lock);
 		err = dev_hard_header(skb, dev, ntohs(skb->protocol),
 				      neigh->ha, NULL, skb->len);