NTFS: 2.1.9 release - Fix two bugs in the decompression engine

      in handling of corner cases.

Documentation/filesystems/ntfs.txt

@@ -273,6 +273,8 @@ ChangeLog
 
 Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog.
 
+2.1.9:
+	- Fix two bugs in handling of corner cases in the decompression engine.
 2.1.8:
 	- Read the $MFT mirror and compare it to the $MFT and if the two do not
 	  match, force a read-only mount and do not allow read-write remounts.

fs/ntfs/ChangeLog

@@ -19,7 +19,19 @@ ToDo:
 	  sufficient for synchronisation here. We then just need to make sure
 	  ntfs_readpage/writepage/truncate interoperate properly with us.
 
-2.1.8 - Handle $MFT mirror and $LogFile, improve time ihandling, and cleanups.
+2.1.9 - Fix two bugs in decompression engine.
+
+	- Fix a bug where we would not always detect that we have reached the
+	  end of a compression block because we were ending at minus one byte
+	  which is effectively the same as being at the end.  The fix is to
+	  check whether the uncompressed buffer has been fully filled and if so
+	  we assume we have reached the end of the compression block.  A big
+	  thank you to Marcin Gibuła for the bug report, the assistance in
+	  tracking down the bug and testing the fix.
+	- Fix a possible bug where when a compressed read is truncated to the
+	  end of the file, the offset inside the last page was not truncated.
+
+2.1.8 - Handle $MFT mirror and $LogFile, improve time handling, and cleanups.
 
 	- Use get_bh() instead of manual atomic_inc() in fs/ntfs/compress.c.
 	- Modify fs/ntfs/time.c::ntfs2utc(), get_current_ntfs_time(), and

fs/ntfs/Makefile

@@ -5,7 +5,7 @@ obj-$(CONFIG_NTFS_FS) += ntfs.o
 ntfs-objs := aops.o attrib.o compress.o debug.o dir.o file.o inode.o logfile.o \
 	     mft.o mst.o namei.o super.o sysctl.o unistr.o upcase.o
 
-EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.8\"
+EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.9\"
 
 ifeq ($(CONFIG_NTFS_DEBUG),y)
 EXTRA_CFLAGS += -DDEBUG

fs/ntfs/compress.c

@@ -197,9 +197,15 @@ static int ntfs_decompress(struct page *dest_pages[], int *dest_index,
 do_next_sb:
 	ntfs_debug("Beginning sub-block at offset = 0x%x in the cb.",
 			cb - cb_start);
-
-	/* Have we reached the end of the compression block? */
-	if (cb == cb_end || !le16_to_cpup((u16*)cb)) {
+	/*
+	 * Have we reached the end of the compression block or the end of the
+	 * decompressed data?  The latter can happen for example if the current
+	 * position in the compression block is one byte before its end so the
+	 * first two checks do not detect it.
+	 */
+	if (cb == cb_end || !le16_to_cpup((u16*)cb) ||
+			(*dest_index == dest_max_index &&
+			*dest_ofs == dest_max_ofs)) {
 		int i;
 
 		ntfs_debug("Completed. Returning success (0).");
@@ -501,7 +507,7 @@ int ntfs_read_compressed_block(struct page *page)
 	 */
 	unsigned int nr_pages = (end_vcn - start_vcn) <<
 			vol->cluster_size_bits >> PAGE_CACHE_SHIFT;
-	unsigned int xpage, max_page, cur_page, cur_ofs, i;
+	unsigned int xpage, max_page, max_ofs, cur_page, cur_ofs, i;
 	unsigned int cb_clusters, cb_max_ofs;
 	int block, max_block, cb_max_page, bhs_size, nr_bhs, err = 0;
 	struct page **pages;
@@ -544,8 +550,11 @@ int ntfs_read_compressed_block(struct page *page)
 	 */
 	max_page = ((VFS_I(ni)->i_size + PAGE_CACHE_SIZE - 1) >>
 			PAGE_CACHE_SHIFT) - offset;
-	if (nr_pages < max_page)
+	max_ofs = (VFS_I(ni)->i_size + PAGE_CACHE_SIZE - 1) & ~PAGE_CACHE_MASK;
+	if (nr_pages < max_page) {
 		max_page = nr_pages;
+		max_ofs = 0;
+	}
 	for (i = 0; i < max_page; i++, offset++) {
 		if (i != xpage)
 			pages[i] = grab_cache_page_nowait(mapping, offset);
@@ -713,8 +722,14 @@ int ntfs_read_compressed_block(struct page *page)
 	cb_max_page >>= PAGE_CACHE_SHIFT;
 
 	/* Catch end of file inside a compression block. */
-	if (cb_max_page > max_page)
-		cb_max_page = max_page;
+	if (cb_max_page >= max_page) {
+		if (cb_max_page > max_page) {
+			cb_max_page = max_page;
+			cb_max_ofs = max_ofs;
+		} else if (cb_max_ofs > max_ofs) {
+			cb_max_ofs = max_ofs;
+		}
+	}
 
 	if (vcn == start_vcn - cb_clusters) {
 		/* Sparse cb, zero out page range overlapping the cb. */