linux-kernel - Re: Creating tasks on restart: userspace vs kernel

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Date:	Tue, 14 Apr 2009 11:16:01 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Oren Laadan <orenl@...columbia.edu>
Cc:	Ingo Molnar <mingo@...e.hu>, containers@...ts.osdl.org,
	Alexey Dobriyan <adobriyan@...il.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Creating tasks on restart: userspace vs kernel

Quoting Oren Laadan (orenl@...columbia.edu):
> For #1, we need to create a new container to begin with. This already
> requires CAP_SYS_ADMIN. Yes, for now we can use some setuid() to create
> a new pid_ns and then do the restart.

This is why I like tagging a pidns with a userid, and requiring that
current->euid==pidns->uid in order to be allowed to set pid in that
pidns.

We require cap_sys_admin wil doing clone(CLONE_NEWPID).  So if we do
that while uid=500, then drop cap_sys_admin, then we can proceed to
create new tasks with specified pids in that pidns.

-serge
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