fs/ntfs3: reject index allocation if $BITMAP is empty but blocks exist

[ Upstream commit 0dc7117d ]

Index allocation requires at least one bit in the $BITMAP attribute to
track usage of index entries. If the bitmap is empty while index blocks
are already present, this reflects on-disk corruption.

syzbot triggered this condition using a malformed NTFS image. During a
rename() operation involving a long filename (which spans multiple
index entries), the empty bitmap allowed the name to be added without
valid tracking. Subsequent deletion of the original entry failed with
-ENOENT, due to unexpected index state.

Reject such cases by verifying that the bitmap is not empty when index
blocks exist.

Reported-by:  <syzbot+b0373017f711c06ada64@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=b0373017f711c06ada64


Fixes: d99208b9 ("fs/ntfs3: cancle set bad inode after removing name fails")
Tested-by:  <syzbot+b0373017f711c06ada64@syzkaller.appspotmail.com>
Signed-off-by: Moon Hee Lee <moonhee.lee.ca@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>