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Date:   Sat, 30 Mar 2019 17:38:55 +0100
From:   Christian Brauner <christian@brauner.io>
To:     Daniel Colascione <dancol@google.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Jann Horn <jannh@google.com>,
        Andrew Lutomirski <luto@kernel.org>,
        David Howells <dhowells@redhat.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Linux API <linux-api@vger.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        Kees Cook <keescook@chromium.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michael Kerrisk-manpages <mtk.manpages@gmail.com>,
        Jonathan Kowalski <bl0pbl33p@gmail.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Nagarathnam Muthusamy <nagarathnam.muthusamy@oracle.com>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Joel Fernandes <joel@joelfernandes.org>
Subject: Re: [PATCH v2 0/5] pid: add pidfd_open()
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On Sat, Mar 30, 2019 at 09:34:02AM -0700, Daniel Colascione wrote:
> On Sat, Mar 30, 2019 at 9:24 AM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > On Sat, Mar 30, 2019 at 9:19 AM Christian Brauner <christian@brauner.io> wrote:
> > >
> > > From pure API perspective that's all I care about: independence of procfs.
> > > Once we have pidfd_open() we can cleanly signal threads etc.
> >
> > But "independence from procfs" means that you damn well don't then do
> > "oh, now I have a pidfd, I want to turn it into a /proc fd and then
> > munge around there".
> >
> > So I'm literally saying that it had better really *be* independent
> > from /proc. It is the standalone version, but it's most definitely
> > also the version that doesn't then give you secret access to /proc.
> 
> Just to be clear, I'm not proposing granting secret access to procfs,
> and as far as I can see, nobody else is either. We've been talking
> about making it easier to avoid races when you happen to want a pidfd
> and a procfs fd that point to the same process, not granting access
> that you didn't have before. If you'd rather not connect procfs and
> pidfds, we can take this functionality off the table.

This is dead! Nothing like this will make it through this tree. I have
no intention of endangering pidfd_send_signal().

Christian