ext4: fix check for block being out of directory size

ext4: fix check for block being out of directory size

The check in __ext4_read_dirblock() for block being outside of directory
size was wrong because it compared block number against directory size
in bytes. Fix it.

Fixes: 65f8ea4cd57d ("ext4: check if directory block is within i_size")
CVE: CVE-2022-1184
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Link: https://lore.kernel.org/r/20220822114832.1482-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>