qpzm - The OI ratio limit rather prevents from enhancing OI ratio.

[sherlock-admin3]

qpzm

Medium

The OI ratio limit rather prevents from enhancing OI ratio.

Summary

The OI ratio limit rather prevents from enhancing OI ratio.

Vulnerability Detail

The OI ratio limit is in effect only when the smaller side is bigger than minOpenInterest. Therefore, it prevents from enhancing the balance of OI ratio when the bigger side is already way bigger than minOpenInterest and the smaller side starts to increase over minOpenInterest.

For example, suppose minOpenInterest is $1M and maxLongOpenInterestCap and maxShortOpenInterestCap are $100M.

1. Traders open long positions up to nearly $100M.
2. If other traders want to open short positions over $1M, they can't because of the OI ratio check.

           if (params.isAdd) {
               // ...
               uint256 minOpenInterest = longOpenInterest.min(shortOpenInterest);
               // @audit OIRatioLimited check does not start until minOpenInterest is greater than longShortOiBottomLimit 
               if (minOpenInterest < symbolConfig.longShortOiBottomLimit) {
                   return;
               }
               // @audit If max open interest is way greater than min open interest, the OIRatioLimited check will prevent the smaller side from increasing
               if (
                   longOpenInterest.max(shortOpenInterest) - minOpenInterest >
                   CalUtils.mulRate(longOpenInterest + shortOpenInterest, symbolConfig.longShortRatioLimit)
               ) {
                   revert Errors.OIRatioLimited();
               }
           }

Impact

The OI ratio check rather results in a bad effect in OI ratio.

Code Snippet

https://github.com/sherlock-audit/2024-05-elfi-protocol/blob/7e0cead5273b386ca7a1f754483dc387671a35c1/elfi-perp-contracts/contracts/process/MarketProcess.sol#L141-L160

Tool used

Manual Review

Recommendation

Delete the OI Ratio check.

[sherlock-admin2]

The protocol team fixed this issue in the following PRs/commits: https://github.com/0xCedar/elfi-perp-contracts/pull/60

[nevillehuang]

Invalid, limits can be freely adjusted by admins, so no time sensitive DoS (not described in issue) and fund locked for more than a week will occur.

[sherlock-admin2]

The Lead Senior Watson signed off on the fix.