linux-kernel - Re: [PATCH v1 1/2] proc: get process file descriptor from /proc/<pid>

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Message-ID: <20181119182038.27obrbpxp54rhfxt@brauner.io>
Date:   Mon, 19 Nov 2018 19:20:43 +0100
From:   Christian Brauner <christian@...uner.io>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, Jann Horn <jannh@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Aleksa Sarai <cyphar@...har.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Daniel Colascione <dancol@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        linux-man <linux-man@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v1 1/2] proc: get process file descriptor from /proc/<pid>

On Mon, Nov 19, 2018 at 07:32:33AM -0800, Andy Lutomirski wrote:
> On Mon, Nov 19, 2018 at 2:33 AM Christian Brauner <christian@...uner.io> wrote:
> >
> > With this patch an open() call on /proc/<pid> will give userspace a handle
> > to struct pid of the process associated with /proc/<pid>. This allows to
> > maintain a stable handle on a process.
> > I have been discussing various approaches extensively during technical
> > conferences this year culminating in a long argument with Eric at Linux
> > Plumbers. The general consensus was that having a handle on a process
> > should be something that is very simple and easy to maintain with the
> > option of being extensible via a more advanced api if the need arises. I
> > believe that this patch is the most simple, dumb, and therefore
> > maintainable solution.
> 
> How does the mechanism you're adding here differ from proc_pid()?

I'm sorry, I am missing the context around proc_pid()?. Are you talking
about the the proc_pid() function in "internal.h"? What exactly is the
proc_pid() mechanism?