Technically speaking it is OK to pass two aliasing mut _pointers_ to a (safe) Rust function because safe Rust can't do anything dangerous with raw pointers; bot

Technically speaking it is OK to pass two aliasing mut _pointers_ to a (safe) Rust function because safe Rust can't do anything dangerous with raw pointers; both dereferencing and writing through a raw pointer require unsafe. If we are talking about references instead, creating two mutable references to the same object in Rust (unsafe or not) immediately causes UB.