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

[Steven J. Magnani]

From: Steve Magnani <steve@xxxxxxxxxxxxxxx>

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. Worse, an attempt to delete
the file causes its directory entry (FID) to be deleted, but because the
driver believes that a hard link to the file remains, the Extended File
Entry (EFE) and all extents of the file itself remain allocated. Since
there is no hard link, after the FID has been deleted all of these blocks
are unreachable (leaked).

A complete solution to this problem involves walking the File Identifiers
in the file's stream directory and freeing all extents allocated to each
named stream (each of which involves a walk of arbitrary length). As the
complete solution is quite complex, for now just settle for retaining the
stream directory attachment during file modification, and being able to
reclaim the blocks of the file, its Extended File Entry, and its Stream
Directory EFE during file deletion.

The UDF structures used by Windows to attach a simple Zone.Identifier
named stream to a file are:
* A stream directory EFE containing an "in ICB" Zone.Identifier FID,
  which references
* An EFE with "in ICB" stream data

For this case, this partial solution reduces the number of blocks leaked
during file deletion to just one (the EFE containing the stream data).

Signed-off-by: Steven J. Magnani <steve@xxxxxxxxxxxxxxx>

--- a/fs/udf/udf_i.h	2019-07-26 11:35:28.257563879 -0500
+++ b/fs/udf/udf_i.h	2019-08-06 14:35:55.579654263 -0500
@@ -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 */
--- a/fs/udf/super.c	2019-07-26 11:35:28.253563792 -0500
+++ b/fs/udf/super.c	2019-08-06 15:04:30.851086957 -0500
@@ -151,9 +151,13 @@ static struct inode *udf_alloc_inode(str
 
 	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;
+	ei->i_locStreamdir.logicalBlockNum = 0xFFFFFFFF;
+	ei->i_locStreamdir.partitionReferenceNum = 0xFFFF;
 	init_rwsem(&ei->i_data_sem);
 	ei->cached_extent.lstart = -1;
 	spin_lock_init(&ei->i_extent_cache_lock);
--- a/fs/udf/inode.c	2019-07-26 11:35:28.253563792 -0500
+++ b/fs/udf/inode.c	2019-08-06 15:04:30.851086957 -0500
@@ -132,7 +132,7 @@ void udf_evict_inode(struct inode *inode
 	struct udf_inode_info *iinfo = UDF_I(inode);
 	int want_delete = 0;
 
-	if (!inode->i_nlink && !is_bad_inode(inode)) {
+	if ((inode->i_nlink == iinfo->i_streamdir) && !is_bad_inode(inode)) {
 		want_delete = 1;
 		udf_setsize(inode, 0);
 		udf_update_inode(inode, IS_SYNC(inode));
@@ -1485,6 +1485,10 @@ reread:
 		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;
+		iinfo->i_locStreamdir.logicalBlockNum = 0xFFFFFFFF;
+		iinfo->i_locStreamdir.partitionReferenceNum = 0xFFFF;
 	} 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;
 	}
 	inode->i_generation = iinfo->i_unique;
 
@@ -1760,9 +1774,19 @@ static int udf_update_inode(struct inode
 		       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);
--- a/fs/udf/ialloc.c	2019-07-26 11:35:28.253563792 -0500
+++ b/fs/udf/ialloc.c	2019-08-06 15:04:30.851086957 -0500
@@ -31,6 +31,7 @@ void udf_free_inode(struct inode *inode)
 	struct super_block *sb = inode->i_sb;
 	struct udf_sb_info *sbi = UDF_SB(sb);
 	struct logicalVolIntegrityDescImpUse *lvidiu = udf_sb_lvidiu(sb);
+	struct udf_inode_info *iinfo = UDF_I(inode);
 
 	if (lvidiu) {
 		mutex_lock(&sbi->s_alloc_mutex);
@@ -42,7 +43,13 @@ void udf_free_inode(struct inode *inode)
 		mutex_unlock(&sbi->s_alloc_mutex);
 	}
 
-	udf_free_blocks(sb, NULL, &UDF_I(inode)->i_location, 0, 1);
+	udf_free_blocks(sb, NULL, &iinfo->i_location, 0, 1);
+	if (iinfo->i_streamdir) {
+		udf_free_blocks(sb, NULL, &iinfo->i_locStreamdir, 0, 1);
+		udf_warn(inode->i_sb,
+			 "Leaking unsupported stream blocks for inode %lu\n",
+			 inode->i_ino);
+	}
 }
 
 struct inode *udf_new_inode(struct inode *dir, umode_t mode)