KingNFT - Unfair distribution while ````stableCollateralTotal```` can not cover all traders' profit

[sherlock-admin2]

KingNFT

medium

Unfair distribution while stableCollateralTotal can not cover all traders' profit

Summary

In the situation that stableCollateralTotal can't cover all traders' profit, traders who close their positions early can get 100% profit, traders who close lately can get less profit, or in the worst case get nothing. This is not a fair distribution design.

Vulnerability Detail

Let's say current stableCollateralTotal = 10rETH, and all traders' profit are like

Alice = 5 rETH
Bob = 5 rETH
Carl = 2 rETH

If Alice and Bob close their position early than Carl, they get all 10ETH. While Carl tries to close his position, there is no penny left. A fair distribution should look like

ratio = 10rETH / 12rETH = 5 / 6
Alice = 5 * 5 / 6 = 25 / 6 = 4.17 rETH
Bob = 5 * 5 / 6 = 25 / 6 = 4.17 rETH
Carl = 2 * 5 / 6 = 1.67 rETH

Impact

In this case, part of users would get far less profit than fair distribution.

Code Snippet

https://github.com/sherlock-audit/2023-12-flatmoney/blob/bba4f077a64f43fbd565f8983388d0e985cb85db/flatcoin-v1/src/LeverageModule.sol#L255

Tool used

Manual Review

Recommendation

see PoC

[nevillehuang]

Request PoC

[sherlock-admin2]

PoC requested from @ydspa

Requests remaining: 8

[sherlock-admin]

1 comment(s) were left on this issue during the judging contest.

takarez commented:

invalid

[nevillehuang]

Since the watson did not reply with a valid PoC, I cannot verify its validity