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    Subject[PATCH 4.14 068/190] fat: dont allow to mount if the FAT length == 0
    Date
    From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

    commit b1b65750b8db67834482f758fc385bfa7560d228 upstream.

    If FAT length == 0, the image doesn't have any data. And it can be the
    cause of overlapping the root dir and FAT entries.

    Also Windows treats it as invalid format.

    Reported-by: syzbot+6f1624f937d9d6911e2d@syzkaller.appspotmail.com
    Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: Marco Elver <elver@google.com>
    Cc: Dmitry Vyukov <dvyukov@google.com>
    Link: http://lkml.kernel.org/r/87r1wz8mrd.fsf@mail.parknet.co.jp
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/fat/inode.c | 6 ++++++
    1 file changed, 6 insertions(+)

    --- a/fs/fat/inode.c
    +++ b/fs/fat/inode.c
    @@ -1512,6 +1512,12 @@ static int fat_read_bpb(struct super_blo
    goto out;
    }

    + if (bpb->fat_fat_length == 0 && bpb->fat32_length == 0) {
    + if (!silent)
    + fat_msg(sb, KERN_ERR, "bogus number of FAT sectors");
    + goto out;
    + }
    +
    error = 0;

    out:

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