Re: [PATCH 1/2] Btrfs: add more valid checks for superblock

On Wed, May 04, 2016 at 03:23:29PM +0200, David Sterba wrote:

On Tue, May 03, 2016 at 09:02:56AM +0800, Qu Wenruo wrote:

quoted

Liu Bo wrote on 2016/05/02 11:15 -0700:

quoted

This adds valid checks for super_total_bytes, super_bytes_used and
super_stripesize.

Reported-by: Vegard Nossum <redacted>
Reported-by: Quentin Casasnovas <redacted>
Signed-off-by: Liu Bo <redacted>
---
 fs/btrfs/disk-io.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 4e47849..988d03f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c

@@ -4120,6 +4120,20 @@ static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
 	 * Hint to catch really bogus numbers, bitflips or so, more exact checks are
 	 * done later
 	 */
+	if (btrfs_super_total_bytes(sb) == 0) {
+		printk(KERN_ERR "BTRFS: total bytes is zero\n");
+		ret = -EINVAL;
+	}

Would it be better if using "6 * nodesize"?

I'd like to use a precious low limit on total bytes, but we don't have 
such value, so 6 nodesize would be good.

An early check can compare against some reasonable value, but the
total_bytes value must be equal to the sum of all device sizes
(disk_total_bytes). I'm not sure if we have enough information to verify
that at this point though.

That's what I had in mind, the problem is that only the first device information is recorded in superblock.

At this moment We have device_num but we don't know the size of other devices.

Thanks,

-liubo