Prevent integer overflow in some gas calculations

libethereum/Executive.cpp

@@ -66,7 +66,7 @@ bool Executive::setup(bytesConstRef _rlp)
 	}
 
 	// Check gas cost is enough.
-	u256 gasCost = m_t.data.size() * c_txDataGas + c_txGas;
+	u256 gasCost = u256(m_t.data.size()) * c_txDataGas + c_txGas;
 
 	if (m_t.gas < gasCost)
 	{

libethereum/Interface.h

@@ -123,7 +123,7 @@ public:
 	virtual Addresses addresses(int _block) const = 0;
 
 	/// Get the fee associated for a transaction with the given data.
-	static u256 txGas(unsigned _dataCount, u256 _gas = 0) { return c_txDataGas * _dataCount + c_txGas + _gas; }
+	static u256 txGas(unsigned _dataCount, u256 _gas = 0) { return u256(c_txDataGas) * _dataCount + c_txGas + _gas; }
 
 	/// Get the remaining gas limit in this block.
 	virtual u256 gasLimitRemaining() const = 0;

libevm/VM.h

@@ -168,13 +168,13 @@ template <class Ext> dev::bytesConstRef dev::eth::VM::go(Ext& _ext, OnOpFunc con
 
 		case Instruction::CALL:
 			require(7);
-			runGas = c_callGas + m_stack[m_stack.size() - 1];
+			runGas = bigint(c_callGas) + m_stack[m_stack.size() - 1];
 			newTempSize = std::max(memNeed(m_stack[m_stack.size() - 6], m_stack[m_stack.size() - 7]), memNeed(m_stack[m_stack.size() - 4], m_stack[m_stack.size() - 5]));
 			break;
 
 		case Instruction::CALLCODE:
 			require(7);
-			runGas = c_callGas + m_stack[m_stack.size() - 1];
+			runGas = bigint(c_callGas) + m_stack[m_stack.size() - 1];
 			newTempSize = std::max(memNeed(m_stack[m_stack.size() - 6], m_stack[m_stack.size() - 7]), memNeed(m_stack[m_stack.size() - 4], m_stack[m_stack.size() - 5]));
 			break;