udf: reduce leakage of blocks related to named streams

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.

Link: https://lore.kernel.org/r/20190814125002.10869-1-steve@digidescorp.com
Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/inode.c

@@ -1485,6 +1485,8 @@ static int udf_read_inode(struct inode *inode, bool hidden_inode)
 		iinfo->i_lenEAttr = le32_to_cpu(fe->lengthExtendedAttr);
 		iinfo->i_lenAlloc = le32_to_cpu(fe->lengthAllocDescs);
 		iinfo->i_checkpoint = le32_to_cpu(fe->checkpoint);
+		iinfo->i_streamdir = 0;
+		iinfo->i_lenStreams = 0;
 	} else {
 		inode->i_blocks = le64_to_cpu(efe->logicalBlocksRecorded) <<
 		    (inode->i_sb->s_blocksize_bits - 9);
@@ -1498,6 +1500,16 @@ static int udf_read_inode(struct inode *inode, bool hidden_inode)
 		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;
 	}
 	inode->i_generation = iinfo->i_unique;
 
@@ -1760,9 +1772,19 @@ static int udf_update_inode(struct inode *inode, int do_sync)
 		       iinfo->i_ext.i_data,
 		       inode->i_sb->s_blocksize -
 					sizeof(struct extendedFileEntry));
-		efe->objectSize = cpu_to_le64(inode->i_size);
+		efe->objectSize =
+			cpu_to_le64(inode->i_size + iinfo->i_lenStreams);
 		efe->logicalBlocksRecorded = cpu_to_le64(lb_recorded);
 
+		if (iinfo->i_streamdir) {
+			struct long_ad *icb_lad = &efe->streamDirectoryICB;
+
+			icb_lad->extLocation =
+				cpu_to_lelb(iinfo->i_locStreamdir);
+			icb_lad->extLength =
+				cpu_to_le32(inode->i_sb->s_blocksize);
+		}
+
 		udf_adjust_time(iinfo, inode->i_atime);
 		udf_adjust_time(iinfo, inode->i_mtime);
 		udf_adjust_time(iinfo, inode->i_ctime);

fs/udf/super.c

@@ -151,9 +151,11 @@ static struct inode *udf_alloc_inode(struct super_block *sb)
 
 	ei->i_unique = 0;
 	ei->i_lenExtents = 0;
+	ei->i_lenStreams = 0;
 	ei->i_next_alloc_block = 0;
 	ei->i_next_alloc_goal = 0;
 	ei->i_strat4096 = 0;
+	ei->i_streamdir = 0;
 	init_rwsem(&ei->i_data_sem);
 	ei->cached_extent.lstart = -1;
 	spin_lock_init(&ei->i_extent_cache_lock);

fs/udf/udf_i.h

@@ -42,12 +42,15 @@ struct udf_inode_info {
 	unsigned		i_efe : 1;	/* extendedFileEntry */
 	unsigned		i_use : 1;	/* unallocSpaceEntry */
 	unsigned		i_strat4096 : 1;
-	unsigned		reserved : 26;
+	unsigned		i_streamdir : 1;
+	unsigned		reserved : 25;
 	union {
 		struct short_ad	*i_sad;
 		struct long_ad		*i_lad;
 		__u8		*i_data;
 	} i_ext;
+	struct kernel_lb_addr	i_locStreamdir;
+	__u64			i_lenStreams;
 	struct rw_semaphore	i_data_sem;
 	struct udf_ext_cache cached_extent;
 	/* Spinlock for protecting extent cache */