bonding: COW before overwriting the destination MAC address

When there is a ptype handler holding a clone of this skb, whose
destination MAC addresse is overwritten, the owner of this handler may
get a corrupted packet.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 912b416b757338896c2731fa7fb03f1a8b87a0a0..7b7ca971672ff259773a6270fddfbc810dcffff9 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1511,9 +1511,13 @@ static struct sk_buff *bond_handle_frame(struct sk_buff *skb)
        if (bond_dev->priv_flags & IFF_MASTER_ALB &&
            bond_dev->priv_flags & IFF_BRIDGE_PORT &&
            skb->pkt_type == PACKET_HOST) {
-               u16 *dest = (u16 *) eth_hdr(skb)->h_dest;
 
-               memcpy(dest, bond_dev->dev_addr, ETH_ALEN);
+               if (unlikely(skb_cow_head(skb,
+                                         skb->data - skb_mac_header(skb)))) {
+                       kfree_skb(skb);
+                       return NULL;
+               }
+               memcpy(eth_hdr(skb)->h_dest, bond_dev->dev_addr, ETH_ALEN);
        }
 
        return skb;