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Submission Details
Severity: medium
Valid

Precision loss in calculation of `UpliftOnlyExample.sol::onAfterRemoveLiquidity()`

ccvascocc

Summary

The calculation of localData.lpTokenDepositValueChange in function onAfterRemoveLiquidity() will have unexpected behaviour. Unless the pool value increases in increments of 100%, value changes will be supressed:

localData.lpTokenDepositValueChange =
(int256(localData.lpTokenDepositValueNow) - int256(localData.lpTokenDepositValue)) /
int256(localData.lpTokenDepositValue);

  • If value increases by 90% -> localData.lpTokenDepositValueChange == 0

  • If value increases by 100% -> localData.lpTokenDepositValueChange == 1

  • If value increases by 190% -> localData.lpTokenDepositValueChange == 1

  • If value increases by 200% -> localData.lpTokenDepositValueChange == 2

  • If value increases by 290% -> localData.lpTokenDepositValueChange == 2

  • ... and so on

Impact

If pool value increases by 99% feePerLP will be charged as the base fee. All succeding fee variables will take into acocunt the base fee instead of a corresponding uplift fee: localData.feeAmount, localData.feePercentage, exitFee, localData.accruedQuantAMMFees[i], localData.accruedFees[i].

Recommendations

Consider measuring value changes in terms of BIPS.

Updates

Lead Judging Commences

n0kto Lead Judge 7 months ago
Submission Judgement Published
Validated
Assigned finding tags:

finding_onAfterRemoveLiquidity_lpTokenDepositValueChange_rounding_error_100%_minimum

Likelihood: High, every call to the function (withdraw) Impact: Low/Medium, uplift fees will be applied only when the price of one asset is doubled but fixed fees will still be collected.

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