netdev - Re: [RFC][PATCH] ns: Syscalls for better namespace sharing control.

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Date:	Mon, 08 Mar 2010 14:24:30 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Daniel Lezcano <daniel.lezcano@...e.fr>,
	Pavel Emelyanov <xemul@...allels.com>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	containers@...ts.linux-foundation.org,
	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>,
	Ben Greear <greearb@...delatech.com>
Subject: Re: [RFC][PATCH] ns: Syscalls for better namespace sharing control.

"Serge E. Hallyn" <serue@...ibm.com> writes:

> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>> Daniel Lezcano <daniel.lezcano@...e.fr> writes:
>> I guess my meaning is I was expecting.
>> child = fork();
>> if (child == 0) {
>> 	execve(...);
>> }
>> waitpid(child);
>> 
>> This puts /bin/sh in the container as well.
>> 
>> I'm not certain about the /proc/self thing I have never encountered that.
>> But I guess if your pid is outside of the pid namespace of that instance
>> of proc /proc/self will be a broken symlink.
>> 
>> Eric
>
> Hmm, worse than a broken symlink, will it be a wrong symlink if just
> the right pid is created in the container?

It won't happen. readlink and followlink are both based on 
task_tgid_nr_ns(current, ns_of_proc).

Which fails if your process is not known in that pid namespace.

Eric
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