From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [REVIEW][PATCH 3/3] vfs: Fix a regression in mounting proc
Date: Wed, 27 Nov 2013 21:01:57 +0100
Message-ID: <20131127200157.GA2089@redhat.com>
References: <20131118140830.GA22075@mail.hallyn.com>
	<20131118180134.GA24156@mail.hallyn.com>
	<87k3g5gnuv.fsf@xmission.com>
	<20131126181043.GA25492@mail.hallyn.com>
	<87siui1z1g.fsf_-_@xmission.com> <87pppmzoin.fsf_-_@xmission.com>
	<20131127161300.GA24773@redhat.com> <871u21oeyr.fsf@xmission.com>
	<20131127194722.GA32673@redhat.com> <87iovdmxl7.fsf@xmission.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
Content-Disposition: inline
In-Reply-To: <87iovdmxl7.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/containers>,
	<mailto:containers-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/containers/>
List-Post: <mailto:containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
List-Help: <mailto:containers-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/containers>,
	<mailto:containers-request-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org?subject=subscribe>
Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Cc: Aditya Kali <adityakali-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
List-Id: containers.vger.kernel.org

On 11/27, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> writes:
>
> > Just to avoid the possible confusion, let me repeat that the fix itsef
> > looks "obviously fine" to me, "i_nlink != 2" looks obviously wrong.
> >
> > I am not arguing with this patch, I am just trying to understand this
> > logic.
> >
> > On 11/27, Eric W. Biederman wrote:
> >>
> >> [... snip ...]
> >
> > Thanks a lot.
> >
> >> For the real concern about jail environments where proc and sysfs are
> >> not mounted at all a fs_visible check is all that is really required,
> >
> > this is what I can't understand...
> >
> > Lets ignore the implementation details. Suppose that proc was never
> > mounted. Then "mount -t proc" should fail after CLONE_NEWUSER | NEWNS?
>
> Yes.

OK, and I agree this makes sense. Just from the code inspection it wasn't
clear to me if this was intended or not. Plus nlink("/proc/sys") == 1 added
more confusion ;)

Thanks to all.

Oleg.