policycoreutils: local privilege escalation via seunshare

seunshare in policycoreutils 2.2.5 is owned by root with 4755 permissions, and executes programs in a way that changes the relationship between the setuid system call and the getresuid saved set-user-ID value, which makes it easier for local users to gain privileges by leveraging a program that mistakenly expected that it could permanently drop privileges.