linux-kernel - Re: [PATCH v10 7/9] proc: move hidepid values to uapi as they are user interface to mount

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Message-ID: <202003281453.CED94974@keescook>
Date:   Sat, 28 Mar 2020 14:53:49 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Alexey Gladkov <gladkov.alexey@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux Security Module <linux-security-module@...r.kernel.org>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        "Dmitry V . Levin" <ldv@...linux.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH v10 7/9] proc: move hidepid values to uapi as they are
 user interface to mount

On Sat, Mar 28, 2020 at 10:25:47PM +0100, Alexey Gladkov wrote:
> On Sat, Mar 28, 2020 at 01:41:02PM -0700, Kees Cook wrote:
>  > diff --git a/include/uapi/linux/proc_fs.h b/include/uapi/linux/proc_fs.h
> > > new file mode 100644
> > > index 000000000000..dc6d717aa6ec
> > > --- /dev/null
> > > +++ b/include/uapi/linux/proc_fs.h
> > > @@ -0,0 +1,13 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > > +#ifndef _UAPI_PROC_FS_H
> > > +#define _UAPI_PROC_FS_H
> > > +
> > > +/* definitions for hide_pid field */
> > > +enum {
> > > +	HIDEPID_OFF            = 0,
> > > +	HIDEPID_NO_ACCESS      = 1,
> > > +	HIDEPID_INVISIBLE      = 2,
> > > +	HIDEPID_NOT_PTRACEABLE = 4,
> > > +};
> > > +
> > > +#endif
> > > -- 
> > > 2.25.2
> > > 
> > 
> > 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).

-- 
Kees Cook