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

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Message-ID: <CALCETrVvHu2dSJs1dpA-2ozGhZGxbGrnYbUuh98rkCdsz42rfg@mail.gmail.com>
Date:   Mon, 19 Nov 2018 07:32:33 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Christian Brauner <christian@...uner.io>
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 Lutomirski <luto@...nel.org>,
        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 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()?