Jovial Ocean Elk - Incorrect use of nagative values in maintained() and margined() function in Position.sol

[sherlock-admin3]

Jovial Ocean Elk

High

Incorrect use of nagative values in maintained() and margined() function in Position.sol

Summary

The maintained() and margin() functions wrongly handle negative collateral values making a path for undercollateralized positions to appear solvent.

Vulnerability Details

https://github.com/sherlock-audit/2025-01-perennial-v2-4-update/blob/main/perennial-v2/packages/core/contracts/types/Position.sol#L211-L217

https://github.com/sherlock-audit/2025-01-perennial-v2-4-update/blob/main/perennial-v2/packages/core/contracts/types/Position.sol#L242-L250

maintained() and margin() functions
collateral is stored as Fixed6 which is signed but later converted to UFIXED6 which is unsigned using UFixed6Lib.unsafeFrom(collateral).
The negative values are wrapped around to large set of numbers due to two representation -100 → 2^256 - 100 which will cause the check to return true for negative collateral.

Impact

Malicious users can maintain positions with negative collaterals bypassing solvency checks.
Malicious actors can also borrow funds without collateralizing.

Tools Used

Manual review.

Recommendations

Revert or return false if collateral is negative unless position is empty.