Submission Details
Severity:
Wrap code in unchecked block
Summary
Certain operations in Lender::borrow will not underflow/overflow. This functions could be refactored as such.
function borrow(Borrow[] calldata borrows) public {
for (uint256 i = 0; i < borrows.length;) {
bytes32 poolId = borrows[i].poolId;
uint256 debt = borrows[i].debt;
uint256 collateral = borrows[i].collateral;
// get the pool info
Pool memory pool = pools[poolId];
// make sure the pool exists
if (pool.lender == address(0)) revert PoolConfig();
// validate the loan
if (debt < pool.minLoanSize) revert LoanTooSmall();
if (debt > pool.poolBalance) revert LoanTooLarge();
if (collateral == 0) revert ZeroCollateral();
// make sure the user isn't borrowing too much
unchecked {
uint256 loanRatio = (debt * 10 ** 18) / collateral;
if (loanRatio > pool.maxLoanRatio) revert RatioTooHigh();
}
// create the loan
Loan memory loan = Loan({
lender: pool.lender,
borrower: msg.sender,
loanToken: pool.loanToken,
collateralToken: pool.collateralToken,
debt: debt,
collateral: collateral,
interestRate: pool.interestRate,
startTimestamp: block.timestamp,
auctionStartTimestamp: type(uint256).max,
auctionLength: pool.auctionLength
});
// update the pool balance
_updatePoolBalance(poolId, pools[poolId].poolBalance - debt);
pools[poolId].outstandingLoans += debt;
// calculate the fees
uint256 fees;
unchecked {
fees = (debt * borrowerFee) / 10000;
}
// transfer fees
IERC20(loan.loanToken).transfer(feeReceiver, fees);
// transfer the loan tokens from the pool to the borrower
IERC20(loan.loanToken).transfer(msg.sender, debt - fees);
// transfer the collateral tokens from the borrower to the contract
IERC20(loan.collateralToken).transferFrom(
msg.sender,
address(this),
collateral
);
loans.push(loan);
unchecked {
i++;
emit Borrowed(
msg.sender,
pool.lender,
loans.length - 1,
debt,
collateral,
pool.interestRate,
block.timestamp
);
}
}
}
This results in a save of 374 units of gas per loop run in execution cost.
Tools Used
VS Code and Foundry
Prize pool breakdown
Total prize
20,000 USDC
nSLOC
70628 USDC / LOC
18,000 USDC
2,000 USDC
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