On 2/15/17 9:31 PM, Darrick J. Wong wrote:
> On Thu, Feb 02, 2017 at 09:54:56AM -0600, Eric Sandeen wrote:
>> Another in the ongoing saga of attribute leaves with zero
>> entries; in this case, if we try to metadump an inode with
>> a zero-entries attribute leaf, the zeroing code will go off
>> the rails and segfault at:
>>
>> memset(&entries[nentries], 0,
>> first_name - (char *)&entries[nentries]);
>>
>> because first_name is null, and we try to memset a large
>> (negative) number.
>
> So what /does/ get metadumped in the !nentries case?
Um, nothing, because it segfaults?
Oh you mean AFTER the patch. :P
> Is it the block
> header and whatever else happens to be on disk? I guess that's useful
> for diagnostic purposes, since we don't know what's really "stale" when
> the block is obviously bad. (I was eyeing zero_stale_data but then
> convinced myself it was fine to just exit.)
Hm, probably worth finding out what reall does happen for this block,
but i'll go ahead & commit this for now just to avoid the segfault.
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
thanks,
-Eric
> --D
>
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>> ---
>>
>> diff --git a/db/metadump.c b/db/metadump.c
>> index 38519f1..66952f6 100644
>> --- a/db/metadump.c
>> +++ b/db/metadump.c
>> @@ -1654,7 +1654,8 @@ process_attr_block(
>> xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &hdr, leaf);
>>
>> nentries = hdr.count;
>> - if (nentries * sizeof(xfs_attr_leaf_entry_t) +
>> + if (nentries == 0 ||
>> + nentries * sizeof(xfs_attr_leaf_entry_t) +
>> xfs_attr3_leaf_hdr_size(leaf) >
>> XFS_ATTR3_RMT_BUF_SPACE(mp, bs)) {
>> if (show_warnings)
>>
>> --
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