Avoid integer overflow in CopyMap.

src/factory.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 608 matching lines @@
 
 
 Handle<Map> Factory::CopyMap(Handle<Map> src,
                              int extra_inobject_properties) {
   Handle<Map> copy = CopyWithPreallocatedFieldDescriptors(src);
   // Check that we do not overflow the instance size when adding the
   // extra inobject properties.
   int instance_size_delta = extra_inobject_properties * kPointerSize;
   int max_instance_size_delta =
       JSObject::kMaxInstanceSize - copy->instance_size();
-  if (instance_size_delta > max_instance_size_delta) {
+  int max_extra_properties = max_instance_size_delta >> kPointerSizeLog2;
+  if (extra_inobject_properties > max_extra_properties) {
     // If the instance size overflows, we allocate as many properties
     // as we can as inobject properties.
     instance_size_delta = max_instance_size_delta;
-    extra_inobject_properties = max_instance_size_delta >> kPointerSizeLog2;
+    extra_inobject_properties = max_extra_properties;
   }
   // Adjust the map with the extra inobject properties.
   int inobject_properties =
       copy->inobject_properties() + extra_inobject_properties;
   copy->set_inobject_properties(inobject_properties);
   copy->set_unused_property_fields(inobject_properties);
   copy->set_instance_size(copy->instance_size() + instance_size_delta);
   copy->set_visitor_id(StaticVisitorBase::GetVisitorId(*copy));
   return copy;
 }
@@ skipping 1143 matching lines @@
   return Handle<Object>::null();
 }
 
 
 Handle<Object> Factory::ToBoolean(bool value) {
   return value ? true_value() : false_value();
 }
 
 
 } }  // namespace v8::internal