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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 30 Mar 2019 09:24:23 -0700
Message-ID: <CAHk-=whcA0kAWGqet9oJdyttjhP7J4PcU2Ly=n_Qyo6rMJNxRg@mail.gmail.com>
Subject: Re: [PATCH v2 0/5] pid: add pidfd_open()
To:     Christian Brauner <christian@brauner.io>
Cc:     Jann Horn <jannh@google.com>, Andrew Lutomirski <luto@kernel.org>,
        David Howells <dhowells@redhat.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
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        "Eric W. Biederman" <ebiederm@xmission.com>,
        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
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        Oleg Nesterov <oleg@redhat.com>,
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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.

And it weorries me a lot that people are trying to play these kinds of
games. I'm just seeing some android patch that adds this horror and
then starts using it.

                      Linus