reentrancy fix

contracts/CEther.sol

@@ -135,8 +135,7 @@ contract CEther is CToken, CEtherInterface {
 
     function doTransferOut(address payable to, uint amount) internal {
         // Send the Ether and revert on failure
-        (bool success, ) = to.call.value(amount)("");
-        require(success, "doTransferOut failed");
+        to.transfer(amount);
     }
 
     function requireNoError(uint errCode, string memory message) internal pure {

contracts/CToken.sol

@@ -709,12 +709,13 @@ contract CToken is CTokenInterface, Exponential, TokenErrorReporter {
          *  On success, the cToken has redeemAmount less of cash.
          *  doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
          */
-        doTransferOut(redeemer, vars.redeemAmount);
 
         /* We write previously calculated values into storage */
         totalSupply = vars.totalSupplyNew;
         accountTokens[redeemer] = vars.accountTokensNew;
 
+        doTransferOut(redeemer, vars.redeemAmount);
+
         /* We emit a Transfer event, and a Redeem event */
         emit Transfer(redeemer, address(this), vars.redeemTokens);
         emit Redeem(redeemer, vars.redeemAmount, vars.redeemTokens);
@@ -809,13 +810,14 @@ contract CToken is CTokenInterface, Exponential, TokenErrorReporter {
          *  On success, the cToken borrowAmount less of cash.
          *  doTransferOut reverts if anything goes wrong, since we can't be sure if side effects occurred.
          */
-        doTransferOut(borrower, borrowAmount);
 
         /* We write the previously calculated values into storage */
         accountBorrows[borrower].principal = vars.accountBorrowsNew;
         accountBorrows[borrower].interestIndex = borrowIndex;
         totalBorrows = vars.totalBorrowsNew;
 
+        doTransferOut(borrower, borrowAmount);
+
         /* We emit a Borrow event */
         emit Borrow(borrower, borrowAmount, vars.accountBorrowsNew, vars.totalBorrowsNew);