Re: [PATCH AUTOSEL 5.10 16/27] btrfs: tree-checker: check item_size for dev_item

[Greg KH]

On Wed, Feb 09, 2022 at 01:40:52PM -0500, Sasha Levin wrote:
> From: Su Yue <l@xxxxxxxxxx>
> 
> [ Upstream commit ea1d1ca4025ac6c075709f549f9aa036b5b6597d ]
> 
> Check item size before accessing the device item to avoid out of bound
> access, similar to inode_item check.
> 
> Signed-off-by: Su Yue <l@xxxxxxxxxx>
> Reviewed-by: David Sterba <dsterba@xxxxxxxx>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  fs/btrfs/tree-checker.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
> index d4a3a56726aa8..4a5ee516845f7 100644
> --- a/fs/btrfs/tree-checker.c
> +++ b/fs/btrfs/tree-checker.c
> @@ -947,6 +947,7 @@ static int check_dev_item(struct extent_buffer *leaf,
>  			  struct btrfs_key *key, int slot)
>  {
>  	struct btrfs_dev_item *ditem;
> +	const u32 item_size = btrfs_item_size(leaf, slot);
>  
>  	if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) {
>  		dev_item_err(leaf, slot,
> @@ -954,6 +955,13 @@ static int check_dev_item(struct extent_buffer *leaf,
>  			     key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
>  		return -EUCLEAN;
>  	}
> +
> +	if (unlikely(item_size != sizeof(*ditem))) {
> +		dev_item_err(leaf, slot, "invalid item size: has %u expect %zu",
> +			     item_size, sizeof(*ditem));
> +		return -EUCLEAN;
> +	}
> +
>  	ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
>  	if (btrfs_device_id(leaf, ditem) != key->offset) {
>  		dev_item_err(leaf, slot,
> -- 
> 2.34.1
> 

This adds a build warning, showing that the backport is not correct, so
I'll go drop this :(

thanks,

greg k-h