linux-kernel - Re: [PATCH] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs

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Message-ID: <CALCETrU487rqcVi_dx5BP4vCo4T+n6BoWtX6_SBVqUsK0eSgdw@mail.gmail.com>
Date:	Fri, 13 Jan 2012 12:19:12 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	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, luto@....edu, mingo@...e.hu,
	akpm@...ux-foundation.org, khilman@...com, borislav.petkov@....com,
	amwang@...hat.com, ak@...ux.intel.com, eric.dumazet@...il.com,
	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
Subject: Re: [PATCH] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from
 granting privs

On Fri, Jan 13, 2012 at 12:13 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, Jan 13, 2012 at 12:05 PM, Andy Lutomirski <luto@...capital.net> wrote:
>>
>> I'm confused.  The patch does "no security context changes on execve".
>
> So that's what I wanted and thought you did, but your comment:
>
>  "With my patch, selinux can already block the execve if it wants"
>
> is what I reacted to. The "selinux *can*" and the "if it wants" part
> was what made my hackles rise.
>
> If it is not about what selinux can and what selinux wants, I'm happy.
> The security manager shouldn't have any choices in the matter. No
> 'can', no 'want'.
>
> Your choice of words made me think your patch had left that door open.

Fair enough.

It's unavoidable that selinux can block the exec, though -- it could
prevent you from reading the file, in which case good luck execing it
:)

I'll respin this so that it doesn't oops if bisected with AppArmor
running.  Any maintainers want to pick it up?

--Andy
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