Submitted by DadeKuma, also found by Tricko and SBSecurity
The math used to calculate how many fees are owed to the user does not allow underflows, but this is a necessary due to how the Uniswap logic works as fees can be negative. This impact adding/removing funds to a position, resulting in permanently locked funds due to a revert.
Similar to Position's fee growth can revert resulting in funds permanently locked but with a different function/root cause, both issues must be fixed separately.
In position.update underflows are not allowed:
https://github.com/code-423n4/2024-08-superposition/blob/4528c9d2dbe1550d2660dac903a8246076044905/pkg/seawater/src/position.rs#L52-L66
While the original Uniswap version allows underflows:
https://github.com/Uniswap/v3-core/blob/d8b1c635c275d2a9450bd6a78f3fa2484fef73eb/contracts/libraries/Position.sol#L61-L76
The issue is that negative fees are expected due to how the formula works. It is explained in detail in this Uniswaps issue here.
This function is used every time a position is updated, so it will be impossible to remove funds from it when the underflow happens because it will revert, resulting in locked funds.
Consider using - to let Rust underflow without errors in release mode:
Alternatively, consider using wrapping_sub.
Uniswap
0xsomeone (judge) commented:
af-afk (Superposition) confirmed 
