code-423n4 / 2022-01-insure-findings

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Gas: Cache `_fee[_target]` in `Parameters.sol:getFeeRate()` #320

Open code423n4 opened 2 years ago

code423n4 commented 2 years ago

Handle

Dravee

Vulnerability details

Impact

SLOADs are expensive

Proof of Concept

Here, _fee[_target] can be loaded twice from storage:

271:     function getFeeRate(address _target)
272:         external
273:         view
274:         override
275:         returns (uint256)
276:     {
277:         if (_fee[_target] == 0) {
278:             return _fee[address(0)];
279:         } else {
280:             return _fee[_target];
281:         }
282:     }

Tools Used

VS Code

Recommended Mitigation Steps

Cache the storage reading in a memory variable

oishun1112 commented 2 years ago

I've confirmed that this implementation

increase gas around 30 when called the default value
reduce gas around 200 when called the set value

most of the cases, this tends to return the default value, so we want to keep the current implementation

oishun1112 commented 2 years ago

we confirm this issue to reduce gas cost in the future

oishun1112 commented 2 years ago

https://github.com/InsureDAO/pool-contracts/pull/49