net: sched: ife: check on metadata length

This patch checks if sk buffer is available to dererence ife header. If
not then NULL will returned to signal an malformed ife packet. This
avoids to crashing the kernel from outside.

Signed-off-by: Alexander Aring <[email protected]>
Reviewed-by: Yotam Gigi <[email protected]>
Acked-by: Jamal Hadi Salim <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Alexander Aring

net/ife/ife.c

@@ -69,6 +69,9 @@ void *ife_decode(struct sk_buff *skb, u16 *metalen)
 	int total_pull;
 	u16 ifehdrln;
 
+	if (!pskb_may_pull(skb, skb->dev->hard_header_len + IFE_METAHDRLEN))
+		return NULL;
+
 	ifehdr = (struct ifeheadr *) (skb->data + skb->dev->hard_header_len);
 	ifehdrln = ntohs(ifehdr->metalen);
 	total_pull = skb->dev->hard_header_len + ifehdrln;