[libvirt-users] Are more then one overlay possible without recieving a "Permission denied"?

[Xen Mann]

I've created a backing chain like this. FirstFollr.ovl is an overlay to Base.img and so on.

Base.img (ok - Win 10 Installation starting)
FirstFloor.ovl (ok - Win 10 Installation starting)
SecondFloor.ovl (permission denied -> Base.img) => assumed Bug
Roof.ovl (permission denied -> Base.img) => assumed Bug

Using virsh / virt-manager, I can only start Base and FirstFloor. Starting Second and Roof are failing.
What's wrong?

Details are described in:
https://bugzilla.redhat.com/show_bug.cgi?id=1588373

System infos:

Compiled against library: libvirt 4.0.0
Using library: libvirt 4.0.0
Using API: QEMU 4.0.0
Running hypervisor: QEMU 2.11.1

Ubuntu 18.04 LTS (Dell Precission Tower 3620)