o Re-enable support of system file flags in jail() by adding back the

o Re-enable support of system file flags in jail() by adding back the
  PRISON_ROOT to the suser_xxx() check.  Since securelevels may now
  be raised in specific jails, use of system flags can still be
  restricted in jail(), but in a more configurable way.
o Users of jail() expecting system flags (such as schg) to restrict
  jail()'s should be sure to set the securelevel appropriately in
  jail()'s.
o This fixes activities involving automated system flag removal in
  jail(), including installkernel and friends.

Obtained from:	TrustedBSD Project