linux-kernel - Re: [PATCH 4/4] Allow unprivileged chroot when safe

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Date:	Mon, 16 Jan 2012 12:18:37 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Colin Walters <walters@...bum.org>
Cc:	Casey Schaufler <casey@...aufler-ca.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jamie Lokier <jamie@...reable.org>,
	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	keescook@...omium.org, john.johansen@...onical.com,
	serge.hallyn@...onical.com, coreyb@...ux.vnet.ibm.com,
	pmoore@...hat.com, eparis@...hat.com, djm@...drot.org,
	segoon@...nwall.com, rostedt@...dmis.org, jmorris@...ei.org,
	scarybeasts@...il.com, avi@...hat.com, penberg@...helsinki.fi,
	viro@...iv.linux.org.uk, mingo@...e.hu, akpm@...ux-foundation.org,
	khilman@...com, borislav.petkov@....com, amwang@...hat.com,
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	gregkh@...e.de, dhowells@...hat.com, daniel.lezcano@...e.fr,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, olofj@...omium.org,
	mhalcrow@...gle.com, dlaor@...hat.com, corbet@....net,
	alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH 4/4] Allow unprivileged chroot when safe

On Mon, Jan 16, 2012 at 11:26 AM, Colin Walters <walters@...bum.org> wrote:
> On Sun, 2012-01-15 at 16:37 -0800, Andy Lutomirski wrote:
>
>> Because chroot is an easy way to break out of chroot jail, CAP_SYS_ADMIN
>> is still required if the caller is already chrooted.
>
> This part is pretty gross.  It means it won't work for stuff like
> containers (systemd-nspawn etc.) and furthermore I have plans that
> involve running OS trees inside a chroot, and this would obviously not
> work for that.

Agreed.

Unprivileged bind mounts would be a much better approach, but that
would need some concept of an unprivileged user owning a namespace.
Maybe the namespace id work would make this work.

--Andy
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