Submission Details
Severity:
Increment loop inside a unchecked block
Summary
Loop in Lender::giveLoan can be increased inside a unchecked block because it's unrealistic the pool will overflow. The following setup can save 59 units of gast in execution cost per loop run.
function giveLoan(
uint256[] calldata loanIds,
bytes32[] calldata poolIds
) external {
for (uint256 i = 0; i < loanIds.length;) {
uint256 loanId = loanIds[i];
bytes32 poolId = poolIds[i];
// get the loan info
Loan memory loan = loans[loanId];
// validate the loan
if (msg.sender != loan.lender) revert Unauthorized();
// get the pool info
Pool memory pool = pools[poolId];
// validate the new loan
if (pool.loanToken != loan.loanToken) revert TokenMismatch();
if (pool.collateralToken != loan.collateralToken)
revert TokenMismatch();
// new interest rate cannot be higher than old interest rate
if (pool.interestRate > loan.interestRate) revert RateTooHigh();
// auction length cannot be shorter than old auction length
if (pool.auctionLength < loan.auctionLength) revert AuctionTooShort();
// calculate the interest
(
uint256 lenderInterest,
uint256 protocolInterest
) = _calculateInterest(loan);
uint256 totalDebt = loan.debt + lenderInterest + protocolInterest;
if (pool.poolBalance < totalDebt) revert PoolTooSmall();
if (totalDebt < pool.minLoanSize) revert LoanTooSmall();
uint256 loanRatio = (totalDebt * 10 ** 18) / loan.collateral;
if (loanRatio > pool.maxLoanRatio) revert RatioTooHigh();
// update the pool balance of the new lender
_updatePoolBalance(poolId, pool.poolBalance - totalDebt);
pools[poolId].outstandingLoans += totalDebt;
// update the pool balance of the old lender
bytes32 oldPoolId = getPoolId(
loan.lender,
loan.loanToken,
loan.collateralToken
);
_updatePoolBalance(
oldPoolId,
pools[oldPoolId].poolBalance + loan.debt + lenderInterest
);
pools[oldPoolId].outstandingLoans -= loan.debt;
// transfer the protocol fee to the governance
IERC20(loan.loanToken).transfer(feeReceiver, protocolInterest);
emit Repaid(
loan.borrower,
loan.lender,
loanId,
loan.debt + lenderInterest + protocolInterest,
loan.collateral,
loan.interestRate,
loan.startTimestamp
);
// update the loan with the new info
loans[loanId].lender = pool.lender;
loans[loanId].interestRate = pool.interestRate;
loans[loanId].startTimestamp = block.timestamp;
loans[loanId].auctionStartTimestamp = type(uint256).max;
loans[loanId].debt = totalDebt;
emit Borrowed(
loan.borrower,
pool.lender,
loanId,
loans[loanId].debt,
loans[loanId].collateral,
pool.interestRate,
block.timestamp
);
unchecked {
i++;
}
}
}
Prize pool breakdown
Total prize
20,000 USDC
nSLOC
70628 USDC / LOC
18,000 USDC
2,000 USDC
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