Staging: batman-adv: Update pointer to ethhdr after skb_copy

We must ensure that all pointer to a socket buffer are updated when we
copy a socket buffer and free our reference to the old one.
Another part of the kernel could also free its reference which maybe
removes the buffer completely. In that situation we would would feed
wrong information to the routing algorithm after the memory area is
written again by someone else.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/batman-adv/routing.c

@@ -614,6 +614,7 @@ int recv_bat_packet(struct sk_buff *skb,
 		skb = skb_copy(skb, GFP_ATOMIC);
 		if (!skb)
 			return NET_RX_DROP;
+		ethhdr = (struct ethhdr *)skb_mac_header(skb);
 		kfree_skb(skb_old);
 	}
 
@@ -639,8 +640,8 @@ static int recv_my_icmp_packet(struct sk_buff *skb)
 	unsigned long flags;
 	uint8_t dstaddr[ETH_ALEN];
 
-	icmp_packet = (struct icmp_packet *) skb->data;
-	ethhdr = (struct ethhdr *) skb_mac_header(skb);
+	icmp_packet = (struct icmp_packet *)skb->data;
+	ethhdr = (struct ethhdr *)skb_mac_header(skb);
 
 	/* add data to device queue */
 	if (icmp_packet->msg_type != ECHO_REQUEST) {
@@ -671,7 +672,9 @@ static int recv_my_icmp_packet(struct sk_buff *skb)
 			skb = skb_copy(skb, GFP_ATOMIC);
 			if (!skb)
 				return NET_RX_DROP;
-			icmp_packet = (struct icmp_packet *) skb->data;
+
+			icmp_packet = (struct icmp_packet *)skb->data;
+			ethhdr = (struct ethhdr *)skb_mac_header(skb);
 			kfree_skb(skb_old);
 		}
 
@@ -732,6 +735,7 @@ static int recv_icmp_ttl_exceeded(struct sk_buff *skb)
 			if (!skb)
 				return NET_RX_DROP;
 			icmp_packet = (struct icmp_packet *) skb->data;
+			ethhdr = (struct ethhdr *)skb_mac_header(skb);
 			kfree_skb(skb_old);
 		}
 
@@ -780,7 +784,7 @@ int recv_icmp_packet(struct sk_buff *skb)
 	if (!is_my_mac(ethhdr->h_dest))
 		return NET_RX_DROP;
 
-	icmp_packet = (struct icmp_packet *) skb->data;
+	icmp_packet = (struct icmp_packet *)skb->data;
 
 	/* packet for me */
 	if (is_my_mac(icmp_packet->dst))
@@ -812,7 +816,8 @@ int recv_icmp_packet(struct sk_buff *skb)
 			skb = skb_copy(skb, GFP_ATOMIC);
 			if (!skb)
 				return NET_RX_DROP;
-			icmp_packet = (struct icmp_packet *) skb->data;
+			icmp_packet = (struct icmp_packet *)skb->data;
+			ethhdr = (struct ethhdr *)skb_mac_header(skb);
 			kfree_skb(skb_old);
 		}
 
@@ -895,7 +900,8 @@ int recv_unicast_packet(struct sk_buff *skb)
 			skb = skb_copy(skb, GFP_ATOMIC);
 			if (!skb)
 				return NET_RX_DROP;
-			unicast_packet = (struct unicast_packet *) skb->data;
+			unicast_packet = (struct unicast_packet *)skb->data;
+			ethhdr = (struct ethhdr *)skb_mac_header(skb);
 			kfree_skb(skb_old);
 		}
 		/* decrement ttl */