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ErrorInstance: keep a lock that the error info callback adds to the error #644

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ErrorInstance: keep a lock that the error info callback adds to the error #644

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ErrorInstance: keep a lock that the error info callback adds to the e…
robobun Sep 12, 2026
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ErrorInstance: a writable non-configurable property still takes the v…
robobun Sep 13, 2026
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33 changes: 27 additions & 6 deletions Source/JavaScriptCore/runtime/ErrorInstance.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -441,6 +441,10 @@ bool ErrorInstance::materializeErrorInfoIfNeeded(VM& vm)
m_errorInfoMaterialized = true;
DeferGCForAWhile deferGC(vm);

// The lazy properties count as present from creation: an error that is already
// non-extensible here still gets them.
bool wasExtensible = isStructureExtensible();

JSValue stack;
if (!m_stackPropertyAlreadyMaterialized)
stack = fn(vm, *m_stackTrace.get(), m_lineColumn.line, m_lineColumn.column, m_sourceURL, this, this->bunErrorData());
Expand All @@ -452,15 +456,32 @@ bool ErrorInstance::materializeErrorInfoIfNeeded(VM& vm)
m_stackString = String();
}

auto attributes = static_cast<unsigned>(PropertyAttribute::DontEnum);

putDirect(vm, vm.propertyNames->line, jsNumber(m_lineColumn.line), attributes);
putDirect(vm, vm.propertyNames->column, jsNumber(m_lineColumn.column), attributes);
// fn can run user code (Error.prepareStackTrace), which can freeze this error or make one
// of these properties non-configurable. putDirect() checks nothing. So a property that is
// absent is not added to an error that became non-extensible, and a non-configurable
// property keeps its attributes. It takes the value only if an assignment could store it.
bool becameNonExtensible = wasExtensible && !isStructureExtensible();
auto putUnlessLocked = [&](PropertyName propertyName, JSValue value) {
unsigned attributes = static_cast<unsigned>(PropertyAttribute::DontEnum);
unsigned currentAttributes;
if (isValidOffset(structure()->get(vm, propertyName, currentAttributes))) {
if (currentAttributes & PropertyAttribute::DontDelete) {
if (currentAttributes & PropertyAttribute::ReadOnlyOrAccessorOrCustomAccessorOrValue)
return;
attributes = currentAttributes;
}
} else if (becameNonExtensible)
return;
putDirect(vm, propertyName, value, attributes);
};

putUnlessLocked(vm.propertyNames->line, jsNumber(m_lineColumn.line));
putUnlessLocked(vm.propertyNames->column, jsNumber(m_lineColumn.column));
if (!m_sourceURL.isEmpty())
putDirect(vm, vm.propertyNames->sourceURL, jsString(vm, WTF::move(m_sourceURL)), attributes);
putUnlessLocked(vm.propertyNames->sourceURL, jsString(vm, WTF::move(m_sourceURL)));

if (!m_stackPropertyAlreadyMaterialized)
putDirect(vm, vm.propertyNames->stack, stack, attributes);
putUnlessLocked(vm.propertyNames->stack, stack);
return true;
}

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