can: Unify droping of invalid tx skbs and netdev stats

To prevent the CAN drivers to operate on invalid socketbuffers the skbs are
now checked and silently dropped at the xmit-function consistently.

Also the netdev stats are consistently using the CAN data length code (dlc)
for [rx|tx]_bytes now.

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index 80ac5631..d124d83 100644
--- a/drivers/net/can/vcan.c
+++ b/drivers/net/can/vcan.c
@@ -47,6 +47,7 @@
 #include <linux/if_arp.h>
 #include <linux/if_ether.h>
 #include <linux/can.h>
+#include <linux/can/dev.h>
 #include <net/rtnetlink.h>
 
 static __initdata const char banner[] =
@@ -70,10 +71,11 @@
 
 static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
 {
+	struct can_frame *cf = (struct can_frame *)skb->data;
 	struct net_device_stats *stats = &dev->stats;
 
 	stats->rx_packets++;
-	stats->rx_bytes += skb->len;
+	stats->rx_bytes += cf->can_dlc;
 
 	skb->protocol  = htons(ETH_P_CAN);
 	skb->pkt_type  = PACKET_BROADCAST;
@@ -85,11 +87,15 @@
 
 static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
 {
+	struct can_frame *cf = (struct can_frame *)skb->data;
 	struct net_device_stats *stats = &dev->stats;
 	int loop;
 
+	if (can_dropped_invalid_skb(dev, skb))
+		return NETDEV_TX_OK;
+
 	stats->tx_packets++;
-	stats->tx_bytes += skb->len;
+	stats->tx_bytes += cf->can_dlc;
 
 	/* set flag whether this packet has to be looped back */
 	loop = skb->pkt_type == PACKET_LOOPBACK;
@@ -103,7 +109,7 @@
 			 * CAN core already did the echo for us
 			 */
 			stats->rx_packets++;
-			stats->rx_bytes += skb->len;
+			stats->rx_bytes += cf->can_dlc;
 		}
 		kfree_skb(skb);
 		return NETDEV_TX_OK;