Its fixed in docker 1.0 since CAP_DAC_READ_SEARCH is no longer available.
Other FS-related threats to container based VMM's that have been discussed:
- subvolume related FS operations (snapshots etc)
- FS ioctl's that accept FS-handles as well (XFS)
- CAP_DAC_READ_SEARCH also defeats chroot and other
bind-mount containers (privileged LXC)
- CAP_MKNOD might be a problem too (still available in docker 1.0) depending on the drivers available in the kernel