[IFB]: Fix crash on input device removal

The input_device pointer is not refcounted, which means the device may
disappear while packets are queued, causing a crash when ifb passes packets
with a stale skb->dev pointer to netif_rx().

Fix by storing the interface index instead and do a lookup where neccessary.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -188,7 +188,7 @@ enum {
  *	@sk: Socket we are owned by
  *	@tstamp: Time we arrived
  *	@dev: Device we arrived on/are leaving by
- *	@input_dev: Device we arrived on
+ *	@iif: ifindex of device we arrived on
  *	@h: Transport layer header
  *	@nh: Network layer header
  *	@mac: Link layer header
@@ -235,7 +235,8 @@ struct sk_buff {
 	struct sock		*sk;
 	struct skb_timeval	tstamp;
 	struct net_device	*dev;
-	struct net_device	*input_dev;
+	int			iif;
+	/* 4 byte hole on 64 bit*/
 
 	union {
 		struct tcphdr	*th;

include/net/pkt_cls.h

@@ -352,10 +352,13 @@ tcf_change_indev(struct tcf_proto *tp, char *indev, struct rtattr *indev_tlv)
 static inline int
 tcf_match_indev(struct sk_buff *skb, char *indev)
 {
+	struct net_device *dev;
+
 	if (indev[0]) {
-		if  (!skb->input_dev)
+		if  (!skb->iif)
 			return 0;
-		if (strcmp(indev, skb->input_dev->name))
+		dev = __dev_get_by_index(skb->iif);
+		if (!dev || strcmp(indev, dev->name))
 			return 0;
 	}