[mm] Delay setting blend weight and design position.

Previously the `blend->weight_vector`, `blend->default_weight_vector`,
and `blend->design_pos` were set early to allocated but uninitialized
memory under the assumption that the memory would eventually be
initialized. However, it is possible that some of the required
keywords may not actually be present, leaving the memory uninitialized.
This is different from a present but invalid table, which would produce
an error.

Reported as
  https://bugs.chromium.org/p/chromium/issues/detail?id=1261762

* src/type1/t1load.c (t1_allocate_blend): Remove early allocation and
initialization.
(parse_blend_design_positions, parse_weight_vector): Parse into local
and assign to blend if valid.
(T1_Open_Face): Check that if a blend exists that it has the weight
vector and design positions.

src/type1/t1load.c

@@ -117,6 +117,9 @@
         goto Exit;
 
       blend->num_default_design_vector = 0;
+      blend->weight_vector = NULL;
+      blend->default_weight_vector = NULL;
+      blend->design_pos[0] = NULL;
 
       face->blend = blend;
     }
@@ -130,14 +133,11 @@
 
 
         /* allocate the blend `private' and `font_info' dictionaries */
-        if ( FT_QNEW_ARRAY( blend->font_infos[1], num_designs     ) ||
-             FT_QNEW_ARRAY( blend->privates  [1], num_designs     ) ||
-             FT_QNEW_ARRAY( blend->bboxes    [1], num_designs     ) ||
-             FT_QNEW_ARRAY( blend->weight_vector, num_designs * 2 ) )
+        if ( FT_QNEW_ARRAY( blend->font_infos[1], num_designs ) ||
+             FT_QNEW_ARRAY( blend->privates  [1], num_designs ) ||
+             FT_QNEW_ARRAY( blend->bboxes    [1], num_designs ) )
           goto Exit;
 
-        blend->default_weight_vector = blend->weight_vector + num_designs;
-
         blend->font_infos[0] = &face->type1.font_info;
         blend->privates  [0] = &face->type1.private_dict;
         blend->bboxes    [0] = &face->type1.font_bbox;
@@ -164,21 +164,6 @@
       blend->num_axis = num_axis;
     }
 
-    /* allocate the blend design pos table if needed */
-    num_designs = blend->num_designs;
-    num_axis    = blend->num_axis;
-    if ( num_designs && num_axis && blend->design_pos[0] == NULL )
-    {
-      FT_UInt  n;
-
-
-      if ( FT_QNEW_ARRAY( blend->design_pos[0], num_designs * num_axis ) )
-        goto Exit;
-
-      for ( n = 1; n < num_designs; n++ )
-        blend->design_pos[n] = blend->design_pos[0] + num_axis * n;
-    }
-
   Exit:
     return error;
 
@@ -872,12 +857,14 @@
   {
     T1_TokenRec  design_tokens[T1_MAX_MM_DESIGNS];
     FT_Int       num_designs;
-    FT_Int       num_axis;
+    FT_Int       num_axis = 0; /* make compiler happy */
     T1_Parser    parser = &loader->parser;
-
+    FT_Memory    memory = face->root.memory;
     FT_Error     error = FT_Err_Ok;
-    PS_Blend     blend;
+    FT_Fixed*    design_pos[T1_MAX_MM_DESIGNS];
+
 
+    design_pos[0] = NULL;
 
     /* get the array of design tokens -- compute number of designs */
     T1_ToTokenArray( parser, design_tokens,
@@ -899,12 +886,10 @@
     {
       FT_Byte*  old_cursor = parser->root.cursor;
       FT_Byte*  old_limit  = parser->root.limit;
-      FT_Int    n;
+      FT_Int    n,nn;
+      PS_Blend  blend;
 
 
-      blend    = face->blend;
-      num_axis = 0;  /* make compiler happy */
-
       FT_TRACE4(( " [" ));
 
       for ( n = 0; n < num_designs; n++ )
@@ -937,7 +922,13 @@
                                      (FT_UInt)num_axis );
           if ( error )
             goto Exit;
-          blend = face->blend;
+
+          /* allocate a blend design pos table */
+          if ( FT_QNEW_ARRAY( design_pos[0], num_designs * num_axis ) )
+            goto Exit;
+
+          for ( nn = 1; nn < num_designs; nn++ )
+            design_pos[nn] = design_pos[0] + num_axis * nn;
         }
         else if ( n_axis != num_axis )
         {
@@ -955,8 +946,8 @@
 
           parser->root.cursor = token2->start;
           parser->root.limit  = token2->limit;
-          blend->design_pos[n][axis] = T1_ToFixed( parser, 0 );
-          FT_TRACE4(( " %f", (double)blend->design_pos[n][axis] / 65536 ));
+          design_pos[n][axis] = T1_ToFixed( parser, 0 );
+          FT_TRACE4(( " %f", (double)design_pos[n][axis] / 65536 ));
         }
         FT_TRACE4(( "]" )) ;
       }
@@ -965,9 +956,21 @@
 
       loader->parser.root.cursor = old_cursor;
       loader->parser.root.limit  = old_limit;
+
+      /* a valid BlendDesignPosition has been parsed */
+      blend = face->blend;
+      if ( blend->design_pos[0] )
+        FT_FREE( blend->design_pos[0] );
+
+      for ( n = 0; n < num_designs; n++ )
+      {
+        blend->design_pos[n] = design_pos[n];
+        design_pos[n] = NULL;
+      }
     }
 
   Exit:
+    FT_FREE( design_pos[0] );
     loader->parser.root.error = error;
   }
 
@@ -1088,6 +1091,7 @@
     T1_TokenRec  design_tokens[T1_MAX_MM_DESIGNS];
     FT_Int       num_designs;
     FT_Error     error  = FT_Err_Ok;
+    FT_Memory    memory = face->root.memory;
     T1_Parser    parser = &loader->parser;
     PS_Blend     blend  = face->blend;
     T1_Token     token;
@@ -1129,6 +1133,12 @@
       goto Exit;
     }
 
+    if ( !blend->weight_vector )
+      if ( FT_QNEW_ARRAY( blend->weight_vector, num_designs * 2 ) )
+        goto Exit;
+
+    blend->default_weight_vector = blend->weight_vector + num_designs;
+
     old_cursor = parser->root.cursor;
     old_limit  = parser->root.limit;
 
@@ -2578,7 +2588,15 @@
          ( !face->blend->num_designs || !face->blend->num_axis ) )
       T1_Done_Blend( face );
 
-    /* another safety check */
+    /* the font may have no valid WeightVector */
+    if ( face->blend && !face->blend->weight_vector )
+      T1_Done_Blend( face );
+
+    /* the font may have no valid BlendDesignPositions */
+    if ( face->blend && !face->blend->design_pos[0] )
+      T1_Done_Blend( face );
+
+    /* the font may have no valid BlendDesignMap */
     if ( face->blend )
     {
       FT_UInt  i;