[BRIDGE] netfilter: memory corruption fix

The bridge-netfilter code will overwrite memory if there is not
headroom in the skb to save the header.  This first showed up when
using Xen with sky2 driver that doesn't allocate the extra space.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 3 deletions

diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 6ccd32b3080..864fbbc7b24 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -40,11 +40,15 @@ int br_dev_queue_push_xmit(struct sk_buff *skb)
         else {
 #ifdef CONFIG_BRIDGE_NETFILTER
                 /* ip_refrag calls ip_fragment, doesn't copy the MAC header. */
-                nf_bridge_maybe_copy_header(skb);
+                if (nf_bridge_maybe_copy_header(skb))
+                        kfree_skb(skb);
+                else
 #endif
-                skb_push(skb, ETH_HLEN);
+                {
+                        skb_push(skb, ETH_HLEN);
 
-                dev_queue_xmit(skb);
+                        dev_queue_xmit(skb);
+                }
         }
 
         return 0;