Beedle - Oracle free perpetual lending

Summary

Vulnerability Details

When fetching data from a storage location, assigning the data to a memory variable causes all fields of the struct/array to be read from storage, which incurs a Gcoldsload (2100 gas) for each field of the struct/array. If the fields are read from the new memory variable, they incur an additional MLOAD rather than a cheap stack read. Instead of declearing the variable with the memory keyword, declaring the variable with the storage keyword and caching any fields that need to be re-read in stack variables, will be much cheaper, only incuring the Gcoldsload for the fields actually read. The only time it makes sense to read the whole struct/array into a memory variable, is if the full struct/array is being returned by the function, is being passed to a function that requires memory, or if the array/struct is being read from another memory array/struct

There are 11 instances of this issue:

• local memory variable Fees.sellProfits(address).params is initialized from storage: Fees.WETH should read data from storage directly

• local memory variable Lender.getLoanDebt(uint256).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.borrow(Borrow[]).pool is initialized from storage: Lender.pools should read data from storage directly

• local memory variable Lender.repay(uint256[]).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.giveLoan(uint256[],bytes32[]).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.giveLoan(uint256[],bytes32[]).pool is initialized from storage: Lender.pools should read data from storage directly

• local memory variable Lender.startAuction(uint256[]).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.buyLoan(uint256,bytes32).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.seizeLoan(uint256[]).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.refinance(Refinance[]).loan is initialized from storage: Lender.loans should read data from storage directly

• local memory variable Lender.refinance(Refinance[]).pool is initialized from storage: Lender.pools should read data from storage directly

Impact

Tools Used

Recommendations

Fetching data from storage directly, don't convert storage to memory