linux-kernel - Re: [PATCH 2/2] groups: Allow unprivileged processes to use setgroups to drop groups

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Date:	Mon, 17 Nov 2014 10:07:30 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	linux-man <linux-man@...r.kernel.org>, "Ted Ts'o" <tytso@....edu>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Josh Triplett <josh@...htriplett.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux API <linux-api@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 2/2] groups: Allow unprivileged processes to use setgroups
 to drop groups

On Nov 17, 2014 3:37 AM, "One Thousand Gnomes"
<gnomes@...rguk.ukuu.org.uk> wrote:
>
> > optional), I can do that too.  The security model of "having a group
> > gives you less privilege than not having it" seems crazy, but
> > nonetheless I can see a couple of easy ways that we can avoid breaking
>
> It's an old pattern of use that makes complete sense in a traditional
> Unix permission world because it's the only way to do "exclude {list}"
> nicely. Our default IMHO shouldn't break this.
>
> > that pattern, no_new_privs being one of them.  I'd like to make sure
> > that nobody sees any other real-world corner case that unprivileged
> > setgroups would break.
>
> Barring the usual risk of people doing improper error checking I don't
> see one immediately.
>
> For containers I think it actually makes sense that the sysctl can be
> applied per container anyway.

We'll probably need per container sysctls some day.

>
> Alan
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