CVE-2025-71098 ip6_gre: make ip6gre_header() robust

In the Linux kernel, the following vulnerability has been resolved: ip6gre: make ip6greheader robust Over the years, syzbot found many ways to crash the kernel in ip6greheader 1. This involves team or bonding drivers ability to dynamically change their dev-neededheadroom and/or dev-hardheaderlen ...