From b1b65750b8db67834482f758fc385bfa7560d228 Mon Sep 17 00:00:00 2001
From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Date: Thu, 4 Jun 2020 16:50:56 -0700
Subject: [PATCH] fat: don't allow to mount if the FAT length == 0
Git-commit: b1b65750b8db67834482f758fc385bfa7560d228
Patch-mainline: v5.8-rc1
References: bsc#1174845
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>
Acked-by: Jan Kara <jack@suse.cz>
---
fs/fat/inode.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index e6e68b2274a5..a0cf99debb1e 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:
--
2.16.4