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

[Eric Sandeen <sandeen@redhat.com>]

On 8/2/17 8:54 AM, Brian Foster wrote:
> 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.

TODO: see if there's any work to do here ;)  Yes, end of bests
to end of block, I think.

>> +	} 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).

Ok, oops, moved most.  thanks.

Dave also points out that I should be checking DIR3_LEAF1_MAGIC
as well.

Thanks,
-Eric

> 
> 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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