sch_sfq: add sanity check for the packet length

The packet length should be checked before the packet data is dereferenced.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_sfq.c

@@ -122,7 +122,11 @@ static unsigned sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb)
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 	{
-		const struct iphdr *iph = ip_hdr(skb);
+		const struct iphdr *iph;
+
+		if (!pskb_network_may_pull(skb, sizeof(*iph)))
+			goto err;
+		iph = ip_hdr(skb);
 		h = (__force u32)iph->daddr;
 		h2 = (__force u32)iph->saddr ^ iph->protocol;
 		if (!(iph->frag_off&htons(IP_MF|IP_OFFSET)) &&
@@ -131,25 +135,32 @@ static unsigned sfq_hash(struct sfq_sched_data *q, struct sk_buff *skb)
 		     iph->protocol == IPPROTO_UDPLITE ||
 		     iph->protocol == IPPROTO_SCTP ||
 		     iph->protocol == IPPROTO_DCCP ||
-		     iph->protocol == IPPROTO_ESP))
+		     iph->protocol == IPPROTO_ESP) &&
+		     pskb_network_may_pull(skb, iph->ihl * 4 + 4))
 			h2 ^= *(((u32*)iph) + iph->ihl);
 		break;
 	}
 	case htons(ETH_P_IPV6):
 	{
-		struct ipv6hdr *iph = ipv6_hdr(skb);
+		struct ipv6hdr *iph;
+
+		if (!pskb_network_may_pull(skb, sizeof(*iph)))
+			goto err;
+		iph = ipv6_hdr(skb);
 		h = (__force u32)iph->daddr.s6_addr32[3];
 		h2 = (__force u32)iph->saddr.s6_addr32[3] ^ iph->nexthdr;
-		if (iph->nexthdr == IPPROTO_TCP ||
-		    iph->nexthdr == IPPROTO_UDP ||
-		    iph->nexthdr == IPPROTO_UDPLITE ||
-		    iph->nexthdr == IPPROTO_SCTP ||
-		    iph->nexthdr == IPPROTO_DCCP ||
-		    iph->nexthdr == IPPROTO_ESP)
+		if ((iph->nexthdr == IPPROTO_TCP ||
+		     iph->nexthdr == IPPROTO_UDP ||
+		     iph->nexthdr == IPPROTO_UDPLITE ||
+		     iph->nexthdr == IPPROTO_SCTP ||
+		     iph->nexthdr == IPPROTO_DCCP ||
+		     iph->nexthdr == IPPROTO_ESP) &&
+		    pskb_network_may_pull(skb, sizeof(*iph) + 4))
 			h2 ^= *(u32*)&iph[1];
 		break;
 	}
 	default:
+err:
 		h = (unsigned long)skb_dst(skb) ^ (__force u32)skb->protocol;
 		h2 = (unsigned long)skb->sk;
 	}