Two identical calls in one proposal not possible

[code423n4]

Lines of code

https://github.com/code-423n4/2022-08-nounsdao/blob/c1c7c6201d0247f92472419ff657b570f9104565/contracts/governance/NounsDAOLogicV2.sol#L313

Vulnerability details

Impact

Because queueOrRevertInternal reverts when the same call (same target, value, data, signature, eta) is already queued, it is not possible to have the same call two times in the same proposal, which can be limiting for some applications.

Proof Of Concept

There is an auction contract for a token with a buy() function. Because the function does not accept an amount parameter, the user has to call it multiple times when he wants to buy multiple tokens.
Alice creates a proposal to buy two of those tokens, i.e. a proposal that has two times exactly the same call. The proposal succeeds and she wants to queue it. However, this reverts and the Nouns DAO does not get this awesome new token.

Recommended Mitigation Steps

Allow the same call multiple times (in the same proposal) or introduce a times parameter to indicate how many times the contract should be called.

[eladmallel]

This is a known limitation of Compound-base governance, therefore we think it's low risk and leaving it as is.