[PATCH RESEND v14 2/6] namei: LOOKUP_IN_ROOT: chroot-like path resolution

[Aleksa Sarai]

On 2019-10-27, Linus Torvalds <torvalds at linux-foundation.org> wrote:
> On Sat, Oct 26, 2019 at 2:58 PM Aleksa Sarai <cyphar at cyphar.com> wrote:
> >
> > +       /* LOOKUP_IN_ROOT treats absolute paths as being relative-to-dirfd. */
> > +       if (flags & LOOKUP_IN_ROOT)
> > +               while (*s == '/')
> > +                       s++;
> > +
> >         /* Figure out the starting path and root (if needed). */
> >         if (*s == '/') {
> >                 error = nd_jump_root(nd);
> 
> So I'm still hung up on this.
> 
> I guess I can't help it, but I look at the above, and it makes me go
> "whoever wrote those tests wasn't thinking".
> 
> It just annoys me how it tests for '/' completely unnecessarily.
> 
> If LOOKUP_IN_ROOT is true, we know the subsequent test for '/' is not
> going to match, because we just removed it. So I look at that code and
> go "that code is doing stupid things".

Okay, fair enough.

> That's why I suggested moving the LOOKUP_IN_ROOT check inside the '/' test.
> 
> Alternatively, just make the logic be
> 
>         if (flags & LOOKUP_IN_ROOT) {
>                .. remove '/'s ...
>         } else if (*s == '/') {
>                 .. handl;e root ..
> 
> and remove the next "else" clause

I've gone with the latter since I think it reads better.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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