Submission Details
Severity:
updating user index in the ``RToken::burn()`` two times consume more gas
Summary
RToken::burn(): https://github.com/Cyfrin/2025-02-raac/blob/main/contracts/core/tokens/RToken.sol#L154.
updating the value of index, two time
Vulnerability Details
the struct is updated each time the user deposit or withdraw, mainly in mint and burn functions
struct UserState {
uint128 index;
}
mapping(address => UserState) private _userState;
the function burn() updates the value of index, two time which cost more gas because it is in storage:
uint256 userBalance = balanceOf(from);
_userState[from].index = index.toUint128(); //here!!
if(amount > userBalance){
amount = userBalance;
}
uint256 amountScaled = amount.rayMul(index);
_userState[from].index = index.toUint128(); // and here!!
_burn(from, amount.toUint128());
if (receiverOfUnderlying != address(this)) {
IERC20(_assetAddress).safeTransfer(receiverOfUnderlying, amount);
}
emit Burn(from, receiverOfUnderlying, amount, index);
Impact
cost more gas for nothing
Tools Used
Manual Review
Recommendations
update the user index just one Time
Prize pool breakdown
Total prize
77,280 USDC
nSLOC
3,86420
USDC / LOC
74,000
3,280
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