ext4: add validity checks for bitmap block numbers

ext4: add validity checks for bitmap block numbers

An privileged attacker can cause a crash by mounting a crafted ext4
image which triggers a out-of-bounds read in the function
ext4_valid_block_bitmap() in fs/ext4/balloc.c.

This issue has been assigned CVE-2018-1093.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199181
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1560782
Reported-by: Wen Xu <wen.xu@gatech.edu>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
(cherry picked from commit 7dac4a1726a9c64a517d595c40e95e2d0d135f6f)

Orabug: 27854373
CVE: CVE-2018-1093

Signed-off-by: Tim Tianyang Chen <tianyang.chen@oracle.com>
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>
conflict:
    fs/ext4/balloc.c
    fs/ext4/ialloc.c
    Missing commit 6a797d2737 and
    EFSCORRUPTED missing. Use EIO instead.

Signed-off-by: Brian Maly <brian.maly@oracle.com>