ext4: always check block group bounds in ext4_init_block_bitmap()

ext4: always check block group bounds in ext4_init_block_bitmap()

commit 819b23f1c501b17b9694325471789e6b5cc2d0d2 upstream.

Regardless of whether the flex_bg feature is set, we should always
check to make sure the bits we are setting in the block bitmap are
within the block group bounds.

https://bugzilla.kernel.org/show_bug.cgi?id=199865

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit ac48bb9bc0a32f5a4432be1645b57607f8c46aa7)

Orabug: 29428607
CVE: CVE-2018-10878

Signed-off-by: John Donnelly <John.P.Donnelly@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>