GitHub https://github.com/Cyfrin/2024-07-zaros/blob/d687fe96bb7ace8652778797052a38763fbcbb1b/src/external/chainlink/ChainlinkUtil.sol#L26-L72

Summary

In ChainlinkUtil, when the getPrice function is called to query the provided Chainlink Price Feed for the margin collateral oracle price, there is no explicit check for the price being equal to zero. Consequently, getPrice can return 0.

The problem arises when deductAccountMargin is called. This function calls marginCollateralConfiguration.getPrice() to obtain the collateral's USD price, which is saved in ctx.marginCollateralPriceUsdX18. This value is then passed to withdrawMarginUsd. Within withdrawMarginUsd, a division occurs: UD60x18 requiredMarginInCollateralX18 = amountUsdX18.div(ctx.marginCollateralPriceUsdX18);. This can lead to a division by zero error.

Impact

A division by zero error will occur, which, in newer versions of Solidity, will cause the transaction to revert. This can lead to a temporary DoS for the liquidateAccounts and fillMarketOrder functions.

Recommendation

Do note that if (answer <= minAnswer || answer >= maxAnswer) { check doesn't stop the price from returning 0 because minAnswer is int192 datatype and can save negative values, so for fixing this issue add a check in getPrice to handle the case where answer is equal to zero. This early return with a proper error will prevent the division by zero case.

In ChainlinkUtil: