Re: [PATCH] xfs_metadump: zap stale date in DIR2_LEAF1 dirs

[Brian Foster <bfoster@redhat.com>]

On Tue, Aug 01, 2017 at 09:35:27PM -0500, Eric Sandeen wrote:
> xfs_metadump attempts to zero out unused regions of metadata
> blocks to prevent data leaks when sharing metadata images.
> 
> However, Stefan Ring reported a significant number of leaked
> strings when dumping his 1T filesystem.  Based on a reduced
> metadata set, I was able to identify "leaf" directories
> (with XFS_DIR2_LEAF1_MAGIC magic) as the primary culprit;
> the region between the end of the entries array and the start
> of the bests array was not getting zeroed out.  This patch
> seems to remedy that problem.
> 
> Reported-by: Stefan Ring <stefanrin@gmail.com>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> I may have missed some handy macro to work out some of the
> math below, if so I'd be perfectly happy to hear about it ;)
> 

Looks good to me. A couple nits...

> diff --git a/db/metadump.c b/db/metadump.c
> index 96641e0..6d77d61 100644
> --- a/db/metadump.c
> +++ b/db/metadump.c
> @@ -1459,6 +1459,37 @@ process_dir_data_block(
>  	int		wantmagic;
>  	struct xfs_dir2_data_hdr *datahdr;
>  
> +	if (offset >= mp->m_dir_geo->freeblk) {
> +		/* TODO */
> +		return;

TODO what exactly? Zero from the end of the bests array to the end of
the block? We could at least add the if (!zero_stale_data) check here
too.

> +	} else if (offset >= mp->m_dir_geo->leafblk) {
> +		struct xfs_dir2_leaf		*leaf;
> +		struct xfs_dir2_leaf_tail	*ltp;
> +		struct xfs_dir3_icleaf_hdr 	leafhdr;
> +
> +		if (!zero_stale_data)
> +			return;
> +
> +		leaf = (struct xfs_dir2_leaf *)block;
> +		ltp = xfs_dir2_leaf_tail_p(mp->m_dir_geo, leaf);

ltp isn't used until the block of code below (which already has locally
scoped vars).

Brian

> +		M_DIROPS(mp)->leaf_hdr_from_disk(&leafhdr, leaf);
> +
> +		/* Zero out space from end of ents[] to bests */
> +		if (leafhdr.magic == XFS_DIR2_LEAF1_MAGIC) {
> +			struct xfs_dir2_leaf_entry	*ents;
> +			__be16				*lbp;
> +			char				*start; /* end of ents */
> +
> +			ents = M_DIROPS(mp)->leaf_ents_p(leaf);
> +			start = (char *)&ents[leafhdr.count + leafhdr.stale];
> +			lbp = xfs_dir2_leaf_bests_p(ltp);
> +			memset(start, 0, (char *)lbp - start);
> +			iocur_top->need_crc = 1;
> +		}
> +		return;
> +	}
> +
> +	/* It's a data block. */
>  	datahdr = (struct xfs_dir2_data_hdr *)block;
>  
>  	if (is_block_format) {
> @@ -1800,9 +1831,6 @@ process_single_fsb_objects(
>  		dp = iocur_top->data;
>  		switch (btype) {
>  		case TYP_DIR2:
> -			if (o >= mp->m_dir_geo->leafblk)
> -				break;
> -
>  			process_dir_data_block(dp, o,
>  					 last == mp->m_dir_geo->fsbcount);
>  			iocur_top->need_crc = 1;
> 
> --
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