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

From: Steve Magnani
Date: Mon Aug 19 2019 - 08:10:29 EST

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:

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.
} 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?

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

#include <standard.disclaimer>