linux-kernel - Re: [PATCH] devpts: Add ptmx_uid and ptmx

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Date:	Tue, 31 Mar 2015 16:17:24 +0200
From:	Alexander Larsson <alexl@...hat.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Andy Lutomirski <luto@...capital.net>, gnome-os-list@...me.org,
	Linux Containers <containers@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	mclasen@...hat.com, "Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] devpts: Add ptmx_uid and ptmx_gid options

On tis, 2015-03-31 at 17:08 +0300, James Bottomley wrote:
> On Tue, 2015-03-31 at 06:59 -0700, Andy Lutomirski wrote:
> > 
> > I don't think that this is correct.  That user can already create a
> > nested userns and map themselves as 0 inside it.  Then they can mount
> > devpts.
> 
> I don't mind if they create a container and control the isolated ttys in
> that sub container in the VPS; that's fine.  I do mind if they get
> access to the ttys in the VPS.
> 
> If you can convince me (and the rest of Linux) that the tty subsystem
> should be mountable by an unprivileged user generally, then what you
> propose is OK.

That is controlled by the general rights to mount stuff. I.e. unless you
have CAP_SYS_ADMIN in the VPS container you will not be able to mount
devpts there. You can only do it in a subcontainer where you got
permissions to mount via using user namespaces.

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
       alexl@...hat.com            alexander.larsson@...il.com 
He's an old-fashioned neurotic master criminal from the Mississippi 
delta. She's a manipulative extravagent widow on her way to prison for a 
murder she didn't commit. They fight crime! 

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