icmp: prevent possible NULL dereferences from icmp_build_probe()

In the Linux kernel, the following vulnerability has been resolved: icmp: prevent possible NULL dereferences from icmp_build_probe() First problem is a double call to __in_dev_get_rcu(), because the second one could return NULL. if (__in_dev_get_rcu(dev) && __in_dev_get_rcu(dev)->ifa_list) Second problem is a read from dev->ip6_ptr with no NULL check: if (!list_empty(&rcu_dereference(dev->ip6_ptr)->addr_list)) Use the correct RCU API to fix these. v2: add missing include <net/addrconf.h>