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>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 912b416b757..7b7ca971672 100644
--- 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;