It's only a problem if the bits of memory you want to enforce special protection rights on (ie: no execute, read only, etc.) is also mapped into the GPU's addre

It's only a problem if the bits of memory you want to enforce special protection rights on (ie: no execute, read only, etc.) is also mapped into the GPU's address space. It's not something that "just happens" normally, it most often requires clear intent to do so, but it can be done.