Yul interpreter: Limit nesting level

test/tools/yulInterpreter/Interpreter.cpp

@@ -247,6 +247,7 @@ void Interpreter::incrementStep()
 
 void ExpressionEvaluator::operator()(Literal const& _literal)
 {
+	incrementStep();
 	static YulString const trueString("true");
 	static YulString const falseString("false");
 
@@ -256,6 +257,7 @@ void ExpressionEvaluator::operator()(Literal const& _literal)
 void ExpressionEvaluator::operator()(Identifier const& _identifier)
 {
 	solAssert(m_variables.count(_identifier.name), "");
+	incrementStep();
 	setValue(m_variables.at(_identifier.name));
 }
 
@@ -326,6 +328,7 @@ void ExpressionEvaluator::evaluateArgs(
 	vector<optional<LiteralKind>> const* _literalArguments
 )
 {
+	incrementStep();
 	vector<u256> values;
 	size_t i = 0;
 	/// Function arguments are evaluated in reverse.
@@ -341,3 +344,13 @@ void ExpressionEvaluator::evaluateArgs(
 	m_values = std::move(values);
 	std::reverse(m_values.begin(), m_values.end());
 }
+
+void ExpressionEvaluator::incrementStep()
+{
+	m_nestingLevel++;
+	if (m_state.maxExprNesting > 0 && m_nestingLevel > m_state.maxExprNesting)
+	{
+		m_state.trace.emplace_back("Maximum expression nesting level reached.");
+		throw ExpressionNestingLimitReached();
+	}
+}

test/tools/yulInterpreter/Interpreter.h

@@ -55,6 +55,10 @@ class TraceLimitReached: public InterpreterTerminatedGeneric
 {
 };
 
+class ExpressionNestingLimitReached: public InterpreterTerminatedGeneric
+{
+};
+
 enum class ControlFlowState
 {
 	Default,
@@ -92,6 +96,7 @@ struct InterpreterState
 	size_t maxTraceSize = 0;
 	size_t maxSteps = 0;
 	size_t numSteps = 0;
+	size_t maxExprNesting = 0;
 	ControlFlowState controlFlowState = ControlFlowState::Default;
 
 	void dumpTraceAndState(std::ostream& _out) const;
@@ -202,6 +207,11 @@ private:
 		std::vector<std::optional<LiteralKind>> const* _literalArguments
 	);
 
+	/// Increment evaluation count, throwing exception if the
+	/// nesting level is beyond the upper bound configured in
+	/// the interpreter state.
+	void incrementStep();
+
 	InterpreterState& m_state;
 	Dialect const& m_dialect;
 	/// Values of variables.
@@ -209,6 +219,8 @@ private:
 	Scope& m_scope;
 	/// Current value of the expression
 	std::vector<u256> m_values;
+	/// Current expression nesting level
+	unsigned m_nestingLevel = 0;
 };
 
 }