add precision checking logic

x/evm/keeper/txutils.go

@@ -75,6 +75,11 @@ func (u *TxUtils) ConvertEthereumTxToCosmosTx(ctx context.Context, ethTx *corety
 	// convert value unit from wei to cosmos fee unit
 	value := types.FromEthersUnit(decimals, ethTx.Value())
 
+	// check if the value is correctly converted without dropping any precision
+	if types.ToEthersUint(decimals, value).Cmp(ethTx.Value()) != 0 {
+		return nil, types.ErrInvalidValue.Wrap("failed to convert value to token unit without dropping precision")
+	}
+
 	// signer
 	chainID := sdk.UnwrapSDKContext(ctx).ChainID()
 	ethChainID := types.ConvertCosmosChainIDToEthereumChainID(chainID)

x/evm/types/decimals.go

@@ -70,7 +70,6 @@ func FromEthersUnit(decimals uint8, val *big.Int) *big.Int {
 	}
 
 	decimalDiff := EtherDecimals - decimals
-
 	exp := new(big.Int).Exp(big.NewInt(10), big.NewInt(int64(decimalDiff)), nil)
 	return new(big.Int).Div(val, exp)
 }