Increased gas cost due to unnecessary automatic underflow checks.
Solidity version 0.8+ comes with implicit overflow and underflow checks on unsigned integers.
When an overflow or an underflow isn't possible (as an example, when a comparison is made before the arithmetic operation, or the operation doesn't depend on user input), some gas can be saved by using an unchecked block.
In ConvexStakingWrapper.sol:_calcRewardIntegral(), bal - rewardRemaining can't underflow at line 222 as the conditional statement line 221 prevents it:
File: ConvexStakingWrapper.sol
221: if (_supply > 0 && (bal - rewardRemaining) > 0) {
222: rewardIntegral = uint128(rewardIntegral) + uint128(((bal - rewardRemaining) * 1e20) / _supply); //@audit-info (bal - rewardRemaining) can't underflow because of above if statement
This substraction should get computed inside an unchecked block and stored in a variable, which would then be used in the checked calculation for rewardIntegral.
Tools Used
VS Code
Recommended Mitigation Steps
Uncheck arithmetic operations when the risk of underflow or overflow is already contained by wrapping them in an unchecked block
Handle
Dravee
Vulnerability details
Impact
Increased gas cost due to unnecessary automatic underflow checks.
Solidity version 0.8+ comes with implicit overflow and underflow checks on unsigned integers.
When an overflow or an underflow isn't possible (as an example, when a comparison is made before the arithmetic operation, or the operation doesn't depend on user input), some gas can be saved by using an
unchecked
block.https://docs.soliditylang.org/en/v0.8.10/control-structures.html#checked-or-unchecked-arithmetic
Proof of Concept
In
ConvexStakingWrapper.sol:_calcRewardIntegral()
,bal - rewardRemaining
can't underflow at line 222 as the conditional statement line 221 prevents it:This substraction should get computed inside an
unchecked
block and stored in a variable, which would then be used in the checked calculation forrewardIntegral
.Tools Used
VS Code
Recommended Mitigation Steps
Uncheck arithmetic operations when the risk of underflow or overflow is already contained by wrapping them in an
unchecked
block