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presenceConditionIfConsistent should check knownBase's structure is i… #1660

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20 changes: 10 additions & 10 deletions Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4486,18 +4486,18 @@ Node* ByteCodeParser::load(

ObjectPropertyCondition ByteCodeParser::presenceConditionIfConsistent(JSObject* knownBase, UniquedStringImpl* uid, PropertyOffset offset, const StructureSet& set)
{
if (set.isEmpty())
return ObjectPropertyCondition();
Structure* structure = knownBase->structure();
unsigned attributes;
PropertyOffset firstOffset = set[0]->getConcurrently(uid, attributes);
if (firstOffset != offset)
PropertyOffset baseOffset = structure->getConcurrently(uid, attributes);
if (offset != baseOffset)
return ObjectPropertyCondition();
for (unsigned i = 1; i < set.size(); ++i) {
unsigned otherAttributes;
PropertyOffset otherOffset = set[i]->getConcurrently(uid, otherAttributes);
if (otherOffset != offset || otherAttributes != attributes)
return ObjectPropertyCondition();
}

// We need to check set contains knownBase's structure because knownBase's GetOwnPropertySlot could normally prevent access
// to this property, for example via a cross-origin restriction check. So unless we've executed this access before we can't assume
// just because knownBase has a property uid at offset we're allowed to access.
if (!set.contains(structure))
return ObjectPropertyCondition();

return ObjectPropertyCondition::presenceWithoutBarrier(knownBase, uid, offset, attributes);
}

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