net: Fix skb_under_panic oops in neigh_resolve_output

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>

1 files changed, 2 insertions, 4 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index baca771caae2..22571488730a 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1301,8 +1301,6 @@ int neigh_resolve_output(struct neighbour *neigh, 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;
@@ -1312,6 +1310,7 @@ int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb)
                         neigh_hh_init(neigh, dst);
 
                 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);
@@ -1342,9 +1341,8 @@ int neigh_connected_output(struct neighbour *neigh, struct sk_buff *skb)
         unsigned int seq;
         int err;
 
-        __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);