Re: [RFC] Null Namespaces

["H. Peter Anvin" <hpa@zytor.com>]

On July 1, 2026 2:49:42 AM PDT, Jori Koolstra <jkoolstra@xs4all.nl> wrote:
>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.

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