Volt Protocol contest - georgypetrov's results

This is a manual upgrade of the sixth item in QA report #86 , per judge @jack-the-pug's assessment of it as a Medium risk issue.

If currentMonth in init is 0, then CPI update will revert, zero div https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L92 https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L174 https://github.com/code-423n4/2022-03-volt/blob/main/contracts/utils/Deviation.sol#L23

1. Zero address check https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/peg/NonCustodialPSM.sol#L105 https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L88
2. Unhandled output https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/pcv/compound/ERC20CompoundPCVDeposit.sol#L31
3. It's better to convert previousMonth to int256, it contains implicit conversion to int256 from int 128 https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L124
4. Misleading comment, it's time from initTimed not contract initialization https://github.com/code-423n4/2022-03-volt/blob/main/contracts/utils/Timed.sol#L49
5. Need to always check LINK balance of oracle, when balance < fee oracle can't make update CPI request https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L150
6. If currentMonth in init is 0, then CPI update will revert, zero div https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L92 https://github.com/code-423n4/2022-03-volt/blob/main/contracts/oracle/ScalingPriceOracle.sol#L174 https://github.com/code-423n4/2022-03-volt/blob/main/contracts/utils/Deviation.sol#L23

1. Immutable instead of constant https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/peg/NonCustodialPSM.sol#L49
2. reason string with length > 32 bytes takes more gas, it increases deployed bytecode size https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/peg/NonCustodialPSM.sol#L277 https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/peg/NonCustodialPSM.sol#L402 https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/peg/NonCustodialPSM.sol#L445
3. Should be immutable https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/volt/Volt.sol#L11 https://github.com/code-423n4/2022-03-volt/blob/f1210bf3151095e4d371c9e9d7682d9031860bbd/contracts/pcv/compound/ERC20CompoundPCVDeposit.sol#L16
4. Can be in single slot, timestamp and duration fit in 128 bits https://github.com/code-423n4/2022-03-volt/blob/main/contracts/utils/Timed.sol#L8-L11