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Date:   Sat, 28 Mar 2020 20:17:05 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Alexey Gladkov <gladkov.alexey@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux API <linux-api@vger.kernel.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Linux Security Module <linux-security-module@vger.kernel.org>,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Daniel Micay <danielmicay@gmail.com>,
        Djalal Harouni <tixxdz@gmail.com>,
        "Dmitry V . Levin" <ldv@altlinux.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        "J . Bruce Fields" <bfields@fieldses.org>,
        Jeff Layton <jlayton@poochiereds.net>,
        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v10 7/9] proc: move hidepid values to uapi as they are
 user interface to mount
Message-ID: <202003282016.19E071712@keescook>
References: <20200327172331.418878-1-gladkov.alexey@gmail.com>
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On Sun, Mar 29, 2020 at 12:00:46AM +0100, Alexey Gladkov wrote:
> On Sat, Mar 28, 2020 at 02:53:49PM -0700, Kees Cook wrote:
> > > > > +/* definitions for hide_pid field */
> > > > > +enum {
> > > > > +	HIDEPID_OFF            = 0,
> > > > > +	HIDEPID_NO_ACCESS      = 1,
> > > > > +	HIDEPID_INVISIBLE      = 2,
> > > > > +	HIDEPID_NOT_PTRACEABLE = 4,
> > > > > +};
> > > > Should the numeric values still be UAPI if there is string parsing now?
> > > 
> > > I think yes, because these are still valid hidepid= values.
> > 
> > But if we don't expose the values, we can do whatever we like with
> > future numbers (e.g. the "is this a value or a bit field?" question).
> 
> Alexey Dobriyan suggested to put these parameters into the UAPI and it
> makes sense because these are user parameters.

Okidokey. :) Anyway, ignore my HIDEPID_MAX idea then, since this could
become a bitfield. Just checking for individual bits is the way to go
for now. Sorry for the noise.

-- 
Kees Cook