linux-kernel - Re: [PATCH] procfs: Do not release pid_ns->proc

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Message-ID: <20100621111554.GJ16877@hawkmoon.kerlabs.com>
Date:	Mon, 21 Jun 2010 13:15:54 +0200
From:	Louis Rilling <Louis.Rilling@...labs.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Linux Containers <containers@...ts.osdl.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] procfs: Do not release pid_ns->proc_mnt too early

On 18/06/10 19:55 +0200, Oleg Nesterov wrote:
> On 06/18, Louis Rilling wrote:
> >
> > On 18/06/10 18:08 +0200, Oleg Nesterov wrote:
> > >
> > > Not sure I ever understood this code. Certainly I can't say I understand
> > > it now. Still, do we really need this circle? I am almost sure the patch
> > > below is not right (and it wasn't tested at all), but could you take a
> > > look?
> >
> > I won't pretend understanding better than you do. Still I can try to give my 2
> > cents.
> >
> > Overall, I don't feel comfortable at being able to have a living proc_mnt
> > with a dead pid_ns.
> 
> Yes, this should be fixed, I already realized this. work->func(ns) is
> called when ns is already fixed.
> 
> Otherwise, nobody should use ns->proc_mount when ns is already dead/freed.

I meant the opposite. proc_mnt can be kept mounted somewhere, and accesses to it
will likely try to access (freed) pid_ns from it.

Thanks,

Louis

-- 
Dr Louis Rilling			Kerlabs
Skype: louis.rilling			Batiment Germanium
Phone: (+33|0) 6 80 89 08 23		80 avenue des Buttes de Coesmes
http://www.kerlabs.com/			35700 Rennes

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