Merge pull request openslide#706 from bgilbert/libtiff

tiff: fix corrupt non-JPEG partial bottom tile row on libtiff 4.7.1

Author: bgilbert

src/openslide-decode-tiff.c

@@ -303,9 +303,14 @@ bool _openslide_tiff_read_tile(struct _openslide_tiff_level *tiffl,
     _openslide_performance_warn_once(&tiffl->warned_read_indirect,
                                      "Using slow libtiff read path for "
                                      "directory %d", tiffl->dir);
+    // artificially limit dest height so libtiff 4.7.1 won't unpad the
+    // bottom row of tiles into the bottom pixels of dest
+    // https://gitlab.com/libtiff/libtiff/-/issues/791
+    uint32_t clipped_h =
+      MIN(tiffl->tile_h, MAX(tiffl->image_h - tile_row * tiffl->tile_h, 0));
     return tiff_read_region(tiff, dest,
                             tile_col * tiffl->tile_w, tile_row * tiffl->tile_h,
-                            tiffl->tile_w, tiffl->tile_h, err);
+                            tiffl->tile_w, clipped_h, err);
   }
 }
 

test/cases/generic-tiff-lzw-partial-tile/CMU-1.tiff.xdelta

@@ -0,0 +1,10 @@
+# libtiff 4.7.1 fails to initialize the relevant portion of the output
+# buffer if we try to fully read a partial bottom tile (not a JPEG one,
+# since we bypass libtiff for those).  valgrind finds the problem but
+# sanitize doesn't.
+base: Generic-TIFF/CMU-1.tiff
+slide: CMU-1.tiff
+success: true
+vendor: generic-tiff
+regions:
+  - [16, 16, 0, 8, 8]