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fat: don't allow to mount if the FAT length == 0

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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>
This commit is contained in:
OGAWA Hirofumi 2020-06-04 16:50:56 -07:00 committed by Greg Kroah-Hartman
parent 248bd0506b
commit cadb31d19d
1 changed files with 6 additions and 0 deletions
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6
fs/fat/inode.c
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@ -1512,6 +1512,12 @@ static int fat_read_bpb(struct super_block *sb, struct fat_boot_sector *b,
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: