ipip: validate header length in ipip_tunnel_xmit

We need the same checks introduced by commit cb9f1b78
("ip: validate header length on virtual device xmit") for
ipip tunnel.

Fixes: cb9f1b78 ("ip: validate header length on virtual device xmit")
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ipip.c

@@ -275,6 +275,9 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb,
 	const struct iphdr  *tiph = &tunnel->parms.iph;
 	u8 ipproto;
 
+	if (!pskb_inet_may_pull(skb))
+		goto tx_error;
+
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		ipproto = IPPROTO_IPIP;