From e0544273b70c1b8f6516e927a2effe222f488445 Mon Sep 17 00:00:00 2001 From: OGAWA Hirofumi Date: Thu, 4 Jun 2020 16:50:56 -0700 Subject: [PATCH] fat: don't allow to mount if the FAT length == 0 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 Signed-off-by: Andrew Morton Cc: Marco Elver Cc: Dmitry Vyukov Link: http://lkml.kernel.org/r/87r1wz8mrd.fsf@mail.parknet.co.jp Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/fat/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/fat/inode.c b/fs/fat/inode.c index d40cbad16659..3d5ad11aacc5 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -1519,6 +1519,12 @@ 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: