linux-kernel - Re: [PATCH linux-cr] nested pid namespaces (v2)

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Message-ID: <20100323064140.GB4242@localdomain>
Date:	Tue, 23 Mar 2010 07:41:41 +0100
From:	Louis Rilling <Louis.Rilling@...labs.com>
To:	Matt Helsley <matthltc@...ibm.com>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	Linux Containers <containers@...ts.osdl.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH linux-cr] nested pid namespaces (v2)

On Mon, Mar 22, 2010 at 12:57:35PM -0700, Matt Helsley wrote:
> On Mon, Mar 22, 2010 at 09:38:00AM -0500, Serge E. Hallyn wrote:
> > Quoting Louis Rilling (Louis.Rilling@...labs.com):
> > > On Fri, Mar 19, 2010 at 04:39:55PM -0500, Serge E. Hallyn wrote:
> > > > Support checkpoint and restart of tasks in nested pid namespaces.  At
> 
> <snip>
> 
> > > It would probably be safer too to use task_active_pid_ns() instead of
> > > task->nsproxy->pid_ns, just in case some PID namespace unsharing like proposed
> > > by Eric makes it to mainline.
> > 
> > The task is frozen though so it shouldn't be able to unshare while being
> > checkpointed, right?  But it's probably better code anyway.
> 
> By the time it reaches checkpoint a frozen task is in the refrigerator
> -- most often in the signal delivery portion of syscall return. So it can't
> be making any new unshare/setns syscalls and any changes to the namespaces
> should be visible.

And what about a task having already unshared its pid namespace (from within
the container)? In this case, all pid-related stuff should be based on
task_active_pid_ns(), and ->nsproxy->pid_ns should be recorded too to correctly
restore pid unsharing.

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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