more review feedback

x/evm/keeper/state_transition.go

@@ -388,12 +388,13 @@ func (k *Keeper) ApplyMessageWithConfig(ctx sdk.Context,
 	rules := cfg.ChainConfig.Rules(big.NewInt(ctx.BlockHeight()), cfg.ChainConfig.MergeNetsplitBlock != nil, uint64(ctx.BlockTime().Unix()))
 	stateDB.Prepare(rules, msg.From, cfg.CoinBase, msg.To, evm.AllPrecompiledAddresses(rules), msg.AccessList)
 
+	value := msg.Value
 	if msg.Value == nil {
-		msg.Value = new(big.Int)
+		value = new(big.Int)
 	}
-	valueUint256, isOverflow := uint256.FromBig(msg.Value)
+	valueUint256, isOverflow := uint256.FromBig(value)
 	if isOverflow {
-		return nil, fmt.Errorf("%v is not a valid uint256", msg.Value)
+		return nil, fmt.Errorf("%v is not a valid uint256", value)
 	}
 
 	if contractCreation {

x/evm/statedb/state_object.go

@@ -128,7 +128,13 @@ func (s *stateObject) SubBalance(amount *uint256.Int) {
 	if amount.Sign() == 0 {
 		return
 	}
-	s.SetBalance(new(uint256.Int).Sub(s.Balance(), amount))
+	// the underflow condition should be checked at higher levels, but
+	// we will guard against it anyway to be safe
+	newBalance, isUnderflow := new(uint256.Int).SubOverflow(s.Balance(), amount)
+	if isUnderflow {
+		return
+	}
+	s.SetBalance(newBalance)
 }
 
 // SetBalance update account balance.