cve request: systemd-machined: information exposure for docker containers

[CAI Qian <caiqian () redhat com>]

Once docker containers register themselves to systemd-machined
by oci-register-machine. Any unprivileged user could run
machinectl to list every single containers running in the host
even if the containers do not belong to this user (including containers
belong to the root user), and access sensitive information associated
with any individual container including its internal IP address, OS
version, running processes, and file path for its rootfs.

$ machinectl status cc8d10c7b9892b75843d200d54d34a3a
cc8d10c7b9892b75843d200d54d34a3a(63633864313063376239383932623735)
           Since: Mon 2016-07-25 17:55:36 UTC; 34s ago
          Leader: 43494 (sleep)
         Service: docker; class container
            Root: /var/mnt/overlay/overlay/0429684e3da515ae4f11b8514c7b20f759613
         Address: 172.17.0.2
                  fe80::42:acff:fe11:2
              OS: Red Hat Enterprise Linux Server 7.2 (Maipo)
            Unit: docker-cc8d10c7b9892b75843d200d54d34a3a9435fe0f65527c254ebfd2d
                  └─43494 sleep 3000

   CAI Qian