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code-423n4 / 2021-09-wildcredit-findings

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Caching state variables in local/memory variables avoids SLOADs to save gas #79

Open code423n4 opened 3 years ago

code423n4 commented 3 years ago

Handle

0xRajeev

Vulnerability details

Impact

There are numerous places across contracts where the same state variables (addresses or other types) are read multiple times or the same external calls are made multiple times within a function. Caching state variables or results from external calls in local/memory variables avoids SLOADs and CALLs to save gas. Warm SLOADs cost 100 gas and CALLs cost 2600 gas after Berlin upgrade. MLOADs cost only 3 gas units.


Proof of Concept

Cache pools[_token].pairToken and poolFee: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/UniswapV3Oracle.sol#L85-L95

Cache minRate, lowRate, highRate and targetUtilization: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/InterestRateModel.sol#L73-L83

Cache tokenA & tokenB: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L88-L99

Cache tokenA & tokenB: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L282-L318

Cache lendingController: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L299-L303

Cache lendingController: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L334-L336

Cache tokenA & tokenB: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L335-L346

Cache uniPosition[_account]: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L450-L458

Cache lendingController, uniV3Helper, tokenA and tokenB: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L452-L465

Cache totalDebtAmount[_token]: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/LendingPair.sol#L522-L525

Cache pendingOwner: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/external/Ownable.sol#L36-L38

Cache lendingController: https://github.com/code-423n4/2021-09-wildcredit/blob/c48235289a25b2134bb16530185483e8c85507f8/contracts/PairFactory.sol#L58-L66

Tools Used

Manual Analysis

Recommended Mitigation Steps

Cache state variables or results from external calls in local/memory variables to save gas.