The kernel rightfully has consolidated path resolution in a few key
places as much as possible -- the internal `struct path` does not suffer
from these issues. I barely modify those places to support null root and
CWD, and because of that consolidation, we shouldn't expect new places
to crop up in the future. (Duplicative path resolution logic is a bad
idea whether or not we have a nascent, little-used NULL-cwd/root code
path.) Therefore, I think existing code review, even among people
totally ignorant of this feature, will protect us --- the vast majority
of code will just be working with `struct path`, and be totally
unaffected by this change.

I actually did laugh out loud reading this. I'm sorry, I can't really
take this argument seriously. May I introduce you to drivers/ for a
start and the history of path lookup exploits of the last - say 10
years.

You have to excuse me but it's a mixture of amusement and slight anger.
Amusement because this is really naive and thus also a bit endearing.
Anger because it single-handedly dismisses how big of an attack surface
and problem space path lookup is. The equivalent of every math
professor's "trivial. excercise left to the reader".