Description: cgroup: Use open-time creds and namespace for migration perm checks
References:
 https://lore.kernel.org/lkml/20211209214707.805617-1-tj@kernel.org/T/
 https://bugzilla.redhat.com/show_bug.cgi?id=2035652
Notes:
Bugs:
upstream:
5.10-upstream-stable:
4.19-upstream-stable:
4.9-upstream-stable:
sid:
5.10-bullseye-security:
4.19-buster-security:
4.9-stretch-security: