Definition range_perm (m: mem) (b: block) (lo hi: Z) (k: perm_kind) (p: permission) : Prop :=
  forall ofs, lo <= ofs < hi -> perm m b ofs k p.

Theorem range_perm_cur: forall m b lo hi k p, range_perm m b lo hi Cur p -> range_perm m b lo hi k p.