FreeBSD -- Kernel memory disclosure with nested jails

Problem Description:
A missing NUL-termination check for the jail_set(2) configration
option “osrelease” may return more bytes when reading the jail
configuration back with jail_get(2) than were originally set.
Impact:
For jails with a non-default setting of children.max > 0 (“nested
jails”) a superuser inside a jail can create a jail and may be able to
read and take advantage of exposed kernel memory.