CVE-2022-48956 ipv6: avoid use-after-free in ip6_fragment()

In the Linux kernel, the following vulnerability has been resolved: ipv6: avoid use-after-free in ip6fragment Blamed commit claimed rcureadlock was held by ip6fragment callers. It seems to not be always true, at least for UDP stack. syzbot reported: BUG: KASAN: use-after-free in ip6dstidev...