map_region and unmap_region could access to invalid memory area since
they don't check the size boundary.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: NDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>