vrf: make sure skb->data contains ip header to make routing

vrf_process_v4_outbound() and vrf_process_v6_outbound() do routing
using ip/ipv6 addresses, but don't make sure the header is available
in skb->data[] (skb_headlen() is less then header size).

Case:

1) igb driver from intel.
2) Packet size is greater then 255.
3) MPLS forwards to VRF device.

So, patch adds pskb_may_pull() calls in vrf_process_v4/v6_outbound()
functions.
Signed-off-by: Peter Kosyh <p.kosyh@gmail.com>
Reviewed-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vrf.c

@@ -165,23 +165,29 @@ static int vrf_ip6_local_out(struct net *net, struct sock *sk,
 static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
 					   struct net_device *dev)
 {
-	const struct ipv6hdr *iph = ipv6_hdr(skb);
+	const struct ipv6hdr *iph;
 	struct net *net = dev_net(skb->dev);
-	struct flowi6 fl6 = {
-		/* needed to match OIF rule */
-		.flowi6_oif = dev->ifindex,
-		.flowi6_iif = LOOPBACK_IFINDEX,
-		.daddr = iph->daddr,
-		.saddr = iph->saddr,
-		.flowlabel = ip6_flowinfo(iph),
-		.flowi6_mark = skb->mark,
-		.flowi6_proto = iph->nexthdr,
-		.flowi6_flags = FLOWI_FLAG_SKIP_NH_OIF,
-	};
+	struct flowi6 fl6;
 	int ret = NET_XMIT_DROP;
 	struct dst_entry *dst;
 	struct dst_entry *dst_null = &net->ipv6.ip6_null_entry->dst;
 
+	if (!pskb_may_pull(skb, ETH_HLEN + sizeof(struct ipv6hdr)))
+		goto err;
+
+	iph = ipv6_hdr(skb);
+
+	memset(&fl6, 0, sizeof(fl6));
+	/* needed to match OIF rule */
+	fl6.flowi6_oif = dev->ifindex;
+	fl6.flowi6_iif = LOOPBACK_IFINDEX;
+	fl6.daddr = iph->daddr;
+	fl6.saddr = iph->saddr;
+	fl6.flowlabel = ip6_flowinfo(iph);
+	fl6.flowi6_mark = skb->mark;
+	fl6.flowi6_proto = iph->nexthdr;
+	fl6.flowi6_flags = FLOWI_FLAG_SKIP_NH_OIF;
+
 	dst = ip6_route_output(net, NULL, &fl6);
 	if (dst == dst_null)
 		goto err;
@@ -237,21 +243,27 @@ static int vrf_ip_local_out(struct net *net, struct sock *sk,
 static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
 					   struct net_device *vrf_dev)
 {
-	struct iphdr *ip4h = ip_hdr(skb);
+	struct iphdr *ip4h;
 	int ret = NET_XMIT_DROP;
-	struct flowi4 fl4 = {
-		/* needed to match OIF rule */
-		.flowi4_oif = vrf_dev->ifindex,
-		.flowi4_iif = LOOPBACK_IFINDEX,
-		.flowi4_tos = RT_TOS(ip4h->tos),
-		.flowi4_flags = FLOWI_FLAG_ANYSRC | FLOWI_FLAG_SKIP_NH_OIF,
-		.flowi4_proto = ip4h->protocol,
-		.daddr = ip4h->daddr,
-		.saddr = ip4h->saddr,
-	};
+	struct flowi4 fl4;
 	struct net *net = dev_net(vrf_dev);
 	struct rtable *rt;
 
+	if (!pskb_may_pull(skb, ETH_HLEN + sizeof(struct iphdr)))
+		goto err;
+
+	ip4h = ip_hdr(skb);
+
+	memset(&fl4, 0, sizeof(fl4));
+	/* needed to match OIF rule */
+	fl4.flowi4_oif = vrf_dev->ifindex;
+	fl4.flowi4_iif = LOOPBACK_IFINDEX;
+	fl4.flowi4_tos = RT_TOS(ip4h->tos);
+	fl4.flowi4_flags = FLOWI_FLAG_ANYSRC | FLOWI_FLAG_SKIP_NH_OIF;
+	fl4.flowi4_proto = ip4h->protocol;
+	fl4.daddr = ip4h->daddr;
+	fl4.saddr = ip4h->saddr;
+
 	rt = ip_route_output_flow(net, &fl4, NULL);
 	if (IS_ERR(rt))
 		goto err;