Re: [RFC] Null Namespaces

[Jori Koolstra <jkoolstra@xs4all.nl>]

On Mon, Jun 29, 2026 at 12:39:56PM +0200, Christian Brauner wrote:
> > 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".

I could easily show you why path lookup is trivial, but I have no space
left in the margins of this email.