Since iptunnel_pull_header() can call pskb_may_pull(),
we must reload any pointer that was related to skb->head.
Fixes: a09a4c8dd1ec ("tunnels: Remove encapsulation offloads on decap") Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com> Signed-off-by: David S. Miller <davem@davemloft.net>