Re: [PATCH v2] udf: reduce leakage of blocks related to named streams

[Steve Magnani]

Jan -


On 8/15/19 7:42 AM, Jan Kara wrote:
> On Wed 14-08-19 07:50:02,  Steven J. Magnani  wrote:
> > Windows is capable of creating UDF files having named streams.
> > One example is the "Zone.Identifier" stream attached automatically
> > to files downloaded from a network. See:
> >    https://msdn.microsoft.com/en-us/library/dn392609.aspx
> >
> > Modification of a file having one or more named streams in Linux causes
> > the stream directory to become detached from the file, essentially leaking
> > all blocks pertaining to the file's streams.
> >
> > Fix by saving off information about an inode's streams when reading it,
> > for later use when its on-disk data is updated.
> > <snip>
> >   	} else {
> >   		inode->i_blocks = le64_to_cpu(efe->logicalBlocksRecorded) <<
> >   		    (inode->i_sb->s_blocksize_bits - 9);
> > @@ -1498,6 +1502,16 @@ reread:
> >   		iinfo->i_lenEAttr = le32_to_cpu(efe->lengthExtendedAttr);
> >   		iinfo->i_lenAlloc = le32_to_cpu(efe->lengthAllocDescs);
> >   		iinfo->i_checkpoint = le32_to_cpu(efe->checkpoint);
> > +
> > +		/* Named streams */
> > +		iinfo->i_streamdir = (efe->streamDirectoryICB.extLength != 0);
> > +		iinfo->i_locStreamdir =
> > +			lelb_to_cpu(efe->streamDirectoryICB.extLocation);
> > +		iinfo->i_lenStreams = le64_to_cpu(efe->objectSize);
> > +		if (iinfo->i_lenStreams >= inode->i_size)
> > +			iinfo->i_lenStreams -= inode->i_size;
> > +		else
> > +			iinfo->i_lenStreams = 0;
> Hum, maybe you could just have i_objectSize instead of i_lenStreams? You
> use the field just to preserve objectSize anyway so there's no point in
> complicating it.

I started making this change and found that it actually complicates things more,
by forcing the driver to update i_objectSize everywhere that i_size is changed.
Are you sure this is what you want?

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 Steven J. Magnani               "I claim this network for MARS!
 www.digidescorp.com              Earthling, return my space modulator!"

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