From f2707f2f614efb80a98eea54b87251c4458abd7b Mon Sep 17 00:00:00 2001
From: Hans Wang <hans@compound.finance>
Date: Thu, 9 Nov 2023 00:49:18 -0800
Subject: [PATCH] add low level support to approveThis as well

---
 contracts/Comet.sol              | 9 ++++++---
 contracts/CometMainInterface.sol | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/contracts/Comet.sol b/contracts/Comet.sol
index 2aa12bc2f..4173101e7 100644
--- a/contracts/Comet.sol
+++ b/contracts/Comet.sol
@@ -783,7 +783,7 @@ contract Comet is CometMainInterface {
     function doTransferIn(address asset, address from, uint amount) nonReentrant internal returns (uint) {
         uint256 preTransferBalance = ERC20(asset).balanceOf(address(this));
         (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(ERC20.transferFrom.selector, from, address(this), amount));
-        if (!success || !(returndata.length == 0 || abi.decode(returndata, (bool)))) {
+        if (!success || (returndata.length != 0 && !abi.decode(returndata, (bool)))) {
             revert TransferInFailed();
         }
         return ERC20(asset).balanceOf(address(this)) - preTransferBalance;
@@ -795,7 +795,7 @@ contract Comet is CometMainInterface {
      */
     function doTransferOut(address asset, address to, uint amount) nonReentrant internal {
         (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(ERC20.transfer.selector, to, amount));
-        if (!success || !(returndata.length == 0 || abi.decode(returndata, (bool)))) {
+        if (!success || (returndata.length != 0 && !abi.decode(returndata, (bool)))) {
             revert TransferOutFailed();
         }
     }
@@ -1287,7 +1287,10 @@ contract Comet is CometMainInterface {
     function approveThis(address manager, address asset, uint amount) override external {
         if (msg.sender != governor) revert Unauthorized();
 
-        ERC20(asset).approve(manager, amount);
+        (bool success, bytes memory returndata) = asset.call(abi.encodeWithSelector(ERC20.approve.selector, manager, amount));
+        if (!success || (returndata.length != 0 && !abi.decode(returndata, (bool)))) {
+            revert ApproveFailed();
+        }
     }
 
     /**
diff --git a/contracts/CometMainInterface.sol b/contracts/CometMainInterface.sol
index b0f67b867..610dfd826 100644
--- a/contracts/CometMainInterface.sol
+++ b/contracts/CometMainInterface.sol
@@ -11,6 +11,7 @@ import "./CometCore.sol";
 abstract contract CometMainInterface is CometCore {
     error Absurd();
     error AlreadyInitialized();
+    error ApproveFailed();
     error BadAsset();
     error BadDecimals();
     error BadDiscount();
@@ -25,6 +26,7 @@ abstract contract CometMainInterface is CometCore {
     error NotForSale();
     error NotLiquidatable();
     error Paused();
+    error ReentrantCallBlocked();
     error SupplyCapExceeded();
     error TimestampTooLarge();
     error TooManyAssets();
@@ -32,7 +34,6 @@ abstract contract CometMainInterface is CometCore {
     error TransferInFailed();
     error TransferOutFailed();
     error Unauthorized();
-    error ReentrantCallBlocked();
 
     event Supply(address indexed from, address indexed dst, uint amount);
     event Transfer(address indexed from, address indexed to, uint amount);