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Date:   Mon, 28 Oct 2019 02:41:15 +1100
From:   Aleksa Sarai <cyphar@cyphar.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Al Viro <viro@zeniv.linux.org.uk>,
        Jeff Layton <jlayton@kernel.org>,
        "J. Bruce Fields" <bfields@fieldses.org>,
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        Shuah Khan <shuah@kernel.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Eric Biederman <ebiederm@xmission.com>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Alexei Starovoitov <ast@kernel.org>,
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Subject: Re: [PATCH RESEND v14 2/6] namei: LOOKUP_IN_ROOT: chroot-like path
 resolution
Message-ID: <20191027154115.ex55njkysey4m6pu@yavin.dot.cyphar.com>
References: <20191026185700.10708-1-cyphar@cyphar.com>
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On 2019-10-27, Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Sat, Oct 26, 2019 at 2:58 PM Aleksa Sarai <cyphar@cyphar.com> wrote:
> >
> > +       /* LOOKUP_IN_ROOT treats absolute paths as being relative-to-di=
rfd. */
> > +       if (flags & LOOKUP_IN_ROOT)
> > +               while (*s =3D=3D '/')
> > +                       s++;
> > +
> >         /* Figure out the starting path and root (if needed). */
> >         if (*s =3D=3D '/') {
> >                 error =3D nd_jump_root(nd);
>=20
> So I'm still hung up on this.
>=20
> 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".
>=20
> It just annoys me how it tests for '/' completely unnecessarily.
>=20
> 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 '/' tes=
t.
>=20
> Alternatively, just make the logic be
>=20
>         if (flags & LOOKUP_IN_ROOT) {
>                .. remove '/'s ...
>         } else if (*s =3D=3D '/') {
>                 .. handl;e root ..
>=20
> and remove the next "else" clause

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

--=20
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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