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

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: [email protected] Signed-off-by: OGAWA Hirofumi <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Cc: Marco Elver <[email protected]> Cc: Dmitry Vyukov <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Linus Torvalds <[email protected]>
zandrey · Jun 5, 2020 · b1b6575 · b1b6575
1 parent ada4ab7
commit b1b6575
Showing 1 changed file with 6 additions and 0 deletions.
diff --git 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: