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.

---

index 166cc7e..70bff87 100644
@@ -342,6 +342,12 @@ static netdev_tx_t at91_start_xmit(struct sk_buff *skb,

struct net_device *dev)
unsigned int mb, prio;
u32 reg_mid, reg_mcr;

+ if (invalid_can_skb(skb)) {
+ kfree_skb(skb);
+ dev->stats.tx_dropped++;
+ return NETDEV_TX_OK;
+ }
+
mb = get_tx_next_mb(priv);
prio = get_tx_next_prio(priv);

index 0ec1524..b0bf359 100644
@@ -318,6 +318,12 @@ static int bfin_can_start_xmit(struct sk_buff *skb,

struct net_device *dev)
u16 val;
int i;

+ if (invalid_can_skb(skb)) {
+ kfree_skb(skb);
+ dev->stats.tx_dropped++;
+ return NETDEV_TX_OK;
+ }
+
netif_stop_queue(dev);

/* fill id */

index 9c5a153..4df3b40 100644
@@ -494,9 +494,8 @@ static netdev_tx_t mcp251x_hard_start_xmit(struct sk_buff

*skb,
return NETDEV_TX_BUSY;
}

- if (skb->len != sizeof(struct can_frame)) {
- dev_err(&spi->dev, "dropping packet - bad length\n");
- dev_kfree_skb(skb);
+ if (invalid_can_skb(skb)) {
+ kfree_skb(skb);
net->stats.tx_dropped++;
return NETDEV_TX_OK;
}

index 542a4f7..3abad97 100644
@@ -249,6 +249,12 @@ static netdev_tx_t sja1000_start_xmit(struct sk_buff *skb,
 	uint8_t dreg;
 	int i;
 
+	if (invalid_can_skb(skb)) {
+		kfree_skb(skb);
+		dev->stats.tx_dropped++;
+		return NETDEV_TX_OK;
+	}
+
 	netif_stop_queue(dev);
 
 	fi = dlc = cf->can_dlc;

index 5c993c2..0ec9859 100644
@@ -477,6 +477,12 @@ static netdev_tx_t ti_hecc_xmit(struct sk_buff *skb,

struct net_device *ndev)
u32 mbxno, mbx_mask, data;
unsigned long flags;

+ if (invalid_can_skb(skb)) {
+ kfree_skb(skb);
+ ndev->stats.tx_dropped++;
+ return NETDEV_TX_OK;
+ }
+
mbxno = get_tx_head_mb(priv);
mbx_mask = BIT(mbxno); spin_lock_irqsave(&priv->mbx_lock, flags);
@@ -491,7 +497,6 @@ static netdev_tx_t ti_hecc_xmit(struct sk_buff *skb, struct net_device *ndev)
spin_unlock_irqrestore(&priv->mbx_lock, flags);

/* Prepare mailbox for transmission */
- data = min_t(u8, cf->can_dlc, 8);
if (cf->can_id & CAN_RTR_FLAG) /* Remote transmission request */
data |= HECC_CANMCF_RTR;
data |= get_tx_head_prio(priv) << 8;

index efbb05c..a375781 100644
@@ -767,6 +767,12 @@ static netdev_tx_t ems_usb_start_xmit(struct sk_buff

*skb, struct net_device *ne
size_t size = CPC_HEADER_SIZE + CPC_MSG_HEADER_LEN
+ sizeof(struct cpc_can_msg);

+ if (invalid_can_skb(skb)) {
+ kfree_skb(skb);
+ stats->tx_dropped++;
+ return NETDEV_TX_OK;
+ }
+
/* create a URB, and a buffer for it, and copy the data to the URB */ urb = usb_alloc_urb(0, GFP_ATOMIC);
if (!urb) {

index 80ac563..66411d5 100644
@@ -70,10 +70,11 @@ MODULE_PARM_DESC(echo, "Echo sent frames (for testing).

Default: 0 (Off)");

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 +86,18 @@ static void vcan_rx(struct sk_buff *skb, struct net_device *dev)

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 (unlikely(skb->len != sizeof(*cf) || cf->can_dlc > 8)) {
+ kfree_skb(skb);
+ stats->tx_dropped++;
+ 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 +111,7 @@ static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
* 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;

index 3db7767..e0703c3 100644
@@ -60,6 +60,14 @@ struct can_priv {
  */
 #define get_can_dlc(i)	(min_t(__u8, (i), 8))
 
+/* check if a given socketbuffer does not contain a valid CAN frame */
+static inline int invalid_can_skb(struct sk_buff *skb)
+{
+	const struct can_frame *cf = (struct can_frame *)skb->data;
+
+	return unlikely(skb->len != sizeof(*cf) || cf->can_dlc > 8);
+}
+
 struct net_device *alloc_candev(int sizeof_priv, unsigned int echo_skb_max);
 void free_candev(struct net_device *dev);