From 064af06385742d510e872d4e75d955ae1377e8d8 Mon Sep 17 00:00:00 2001
From: emilio <emilio@ethlend.io>
Date: Wed, 28 Oct 2020 11:47:01 +0100
Subject: [PATCH 1/2] updated percentageMath

---
 contracts/libraries/math/WadRayMath.sol | 29 +++++++++----------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/contracts/libraries/math/WadRayMath.sol b/contracts/libraries/math/WadRayMath.sol
index a1a8d8f4..48985580 100644
--- a/contracts/libraries/math/WadRayMath.sol
+++ b/contracts/libraries/math/WadRayMath.sol
@@ -54,15 +54,13 @@ library WadRayMath {
    * @return the result of a*b, in wad
    **/
   function wadMul(uint256 a, uint256 b) internal pure returns (uint256) {
-    if (a == 0) {
+    if (a == 0 || b == 0) {
       return 0;
     }
 
-    uint256 result = a * b + halfWAD;
+    require(a <= (type(uint256).max-halfWAD)/b, Errors.MULTIPLICATION_OVERFLOW);
 
-    require(result >= halfWAD && (result - halfWAD) / a == b, Errors.MULTIPLICATION_OVERFLOW);
-
-    return result / WAD;
+    return (a * b + halfWAD) / WAD;
   }
 
   /**
@@ -73,14 +71,11 @@ library WadRayMath {
    **/
   function wadDiv(uint256 a, uint256 b) internal pure returns (uint256) {
     require(b != 0, Errors.DIVISION_BY_ZERO);
-
     uint256 halfB = b / 2;
 
-    uint256 result = a * WAD + halfB;
+    require(a <= (type(uint256).max-halfB)/WAD, Errors.MULTIPLICATION_OVERFLOW);
 
-    require(result >= halfB && (result - halfB) / WAD == a, Errors.MULTIPLICATION_OVERFLOW);
-
-    return result / b;
+    return (a * WAD + halfB) / b;
   }
 
   /**
@@ -90,15 +85,14 @@ library WadRayMath {
    * @return the result of a*b, in ray
    **/
   function rayMul(uint256 a, uint256 b) internal pure returns (uint256) {
-    if (a == 0) {
+    if (a == 0 || b == 0) {
       return 0;
     }
 
-    uint256 result = a * b + halfRAY;
+    require(a <= (type(uint256).max-halfRAY)/b, Errors.MULTIPLICATION_OVERFLOW);
 
-    require(result >= halfRAY && (result - halfRAY) / a == b, Errors.MULTIPLICATION_OVERFLOW);
+    return (a * b + halfRAY) / RAY;
 
-    return result / RAY;
   }
 
   /**
@@ -109,14 +103,11 @@ library WadRayMath {
    **/
   function rayDiv(uint256 a, uint256 b) internal pure returns (uint256) {
     require(b != 0, Errors.DIVISION_BY_ZERO);
-
     uint256 halfB = b / 2;
 
-    uint256 result = a * RAY + halfB;
+    require(a <= (type(uint256).max-halfB)/RAY, Errors.MULTIPLICATION_OVERFLOW);
 
-    require(result >= halfB && (result - halfB) / RAY == a, Errors.MULTIPLICATION_OVERFLOW);
-
-    return result / b;
+    return (a * RAY + halfB) / b;
   }
 
   /**

From e91e3595d6c5e82d294e15f3ca2225730ad581f7 Mon Sep 17 00:00:00 2001
From: emilio <emilio@ethlend.io>
Date: Wed, 28 Oct 2020 12:39:11 +0100
Subject: [PATCH 2/2] Updated PercentageMath

---
 contracts/libraries/math/PercentageMath.sol | 22 +++++----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/contracts/libraries/math/PercentageMath.sol b/contracts/libraries/math/PercentageMath.sol
index b853f1db..52a38cd4 100644
--- a/contracts/libraries/math/PercentageMath.sol
+++ b/contracts/libraries/math/PercentageMath.sol
@@ -22,19 +22,13 @@ library PercentageMath {
    * @return the percentage of value
    **/
   function percentMul(uint256 value, uint256 percentage) internal pure returns (uint256) {
-    if (value == 0) {
+    if (value == 0 || percentage == 0) {
       return 0;
     }
 
-    uint256 result = value * percentage;
+    require(value <= (type(uint256).max - HALF_PERCENT)/percentage, Errors.MULTIPLICATION_OVERFLOW);
 
-    require(result / value == percentage, Errors.MULTIPLICATION_OVERFLOW);
-
-    result += HALF_PERCENT;
-
-    require(result >= HALF_PERCENT, Errors.ADDITION_OVERFLOW);
-
-    return result / PERCENTAGE_FACTOR;
+    return (value * percentage + HALF_PERCENT) / PERCENTAGE_FACTOR;
   }
 
   /**
@@ -47,14 +41,8 @@ library PercentageMath {
     require(percentage != 0, Errors.DIVISION_BY_ZERO);
     uint256 halfPercentage = percentage / 2;
 
-    uint256 result = value * PERCENTAGE_FACTOR;
+    require(value <= (type(uint256).max - halfPercentage)/PERCENTAGE_FACTOR, Errors.MULTIPLICATION_OVERFLOW);
 
-    require(result / PERCENTAGE_FACTOR == value, Errors.MULTIPLICATION_OVERFLOW);
-
-    result += halfPercentage;
-
-    require(result >= halfPercentage, Errors.ADDITION_OVERFLOW);
-
-    return result / percentage;
+    return (value * PERCENTAGE_FACTOR + halfPercentage) / percentage;
   }
 }