I've done incautiously
docker run -v /:/mnt:ro someimage
It has resulted with some docker (docker v1.7) daemon error. Since then I can only boot in permissive mode and got lot of selinux errors. Most noticeable one is concerning unable to start journal service.
I've tried to do the relabelling ie by
fixfiles relabel but with no success. Since it happened on Fedora 21, I've also tried to do the upgrade to F22 (all in enforcing=0) but after the upgrade problem still exists. Now have no clue how to find the proper way of fixing this.