Document the potential for jail escape.
From r224615:
Always disable mount and unmount for jails with enforce_statfs==2.
From r231267:
A new jail(8) option "devfs_ruleset" defines the ruleset enforcement for
mounting devfs inside jails. A value of -1 disables mounting devfs in
jails, a value of zero means no restrictions. Nested jails can only
have mounting devfs disabled or inherit parent's enforcement as jails are
not allowed to view or manipulate devfs(8) rules.
From r232059:
To improve control over the use of mount(8) inside a jail(8), introduce
a new jail parameter node with the following parameters:
allow.mount.devfs:
allow mounting the devfs filesystem inside a jail
allow.mount.nullfs:
allow mounting the nullfs filesystem inside a jail
From r232186:
allow.mount.zfs:
allow mounting the zfs filesystem inside a jail
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