From f0cffd840d63654d676a89ea7061d1c2f8e428ae Mon Sep 17 00:00:00 2001
From: mingda <leimingda@pku.edu.cn>
Date: Fri, 25 Sep 2020 10:51:03 +0800
Subject: [PATCH] [trail of bits audit] #1 Loss of precision may allow an
 attacker to get funds for free

---
 contracts/impl/Pricing.sol    | 3 ++-
 contracts/lib/DecimalMath.sol | 5 +++++
 contracts/lib/SafeMath.sol    | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/contracts/impl/Pricing.sol b/contracts/impl/Pricing.sol
index f9ce3ee..ce45235 100644
--- a/contracts/impl/Pricing.sol
+++ b/contracts/impl/Pricing.sol
@@ -14,6 +14,7 @@ import {DODOMath} from "../lib/DODOMath.sol";
 import {Types} from "../lib/Types.sol";
 import {Storage} from "./Storage.sol";
 
+
 /**
  * @title Pricing
  * @author DODO Breeder
@@ -84,7 +85,7 @@ contract Pricing is Storage {
         uint256 Q2 = DODOMath._SolveQuadraticFunctionForTrade(
             targetQuoteAmount,
             quoteBalance,
-            DecimalMath.mul(i, amount),
+            DecimalMath.mulCeil(i, amount),
             true,
             _K_
         );
diff --git a/contracts/lib/DecimalMath.sol b/contracts/lib/DecimalMath.sol
index a121d24..99debb1 100644
--- a/contracts/lib/DecimalMath.sol
+++ b/contracts/lib/DecimalMath.sol
@@ -10,6 +10,7 @@ pragma experimental ABIEncoderV2;
 
 import {SafeMath} from "./SafeMath.sol";
 
+
 /**
  * @title DecimalMath
  * @author DODO Breeder
@@ -25,6 +26,10 @@ library DecimalMath {
         return target.mul(d) / ONE;
     }
 
+    function mulCeil(uint256 target, uint256 d) internal pure returns (uint256) {
+        return target.mul(d).divCeil(ONE);
+    }
+
     function divFloor(uint256 target, uint256 d) internal pure returns (uint256) {
         return target.mul(ONE).div(d);
     }
diff --git a/contracts/lib/SafeMath.sol b/contracts/lib/SafeMath.sol
index f543fb4..dc5bb8d 100644
--- a/contracts/lib/SafeMath.sol
+++ b/contracts/lib/SafeMath.sol
@@ -8,6 +8,7 @@
 pragma solidity 0.6.9;
 pragma experimental ABIEncoderV2;
 
+
 /**
  * @title SafeMath
  * @author DODO Breeder