linux-kernel - Re: [PATCH v6 0/3] security: Yama LSM

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Message-ID: <CAGXu5jJk7uqDY1jkh-Sxz9iVk_rhmdoe7-4yc7QRCZEjrH7UOA@mail.gmail.com>
Date:	Fri, 18 Nov 2011 15:18:23 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH v6 0/3] security: Yama LSM

On Thu, Nov 17, 2011 at 8:17 PM, James Morris <jmorris@...ei.org> wrote:
> On Wed, 26 Oct 2011, Kees Cook wrote:
>
>> As discussed at the Linux Security Summit, I'm resubmitting this
>> code. As an LSM, it has coherent policy around expanding specific DAC
>> behaviors. There is no need for it to be a full-blown MAC, since it is
>> not intended to be one, but rather to be a simplified expansion to DAC,
>> with system-wide knobs. See the specific patches for details...
>
> In principle, Yama can be merged, however there are features with
> unresolved upstream naks:
>
> - Handling symlinks in sticky directories

Also hardlink restrictions (disallow hardlinking to anything that a
user doesn't have read/write access to -- breaks no software, solves
actual vulnerabilities).

> - The ptrace tracker
>
> These still need to be resolved.

Hi Al,

I know you're not a fan of LSMs in general, but can you let Yama
extend DAC in these two cases (symlink and hardlink restrictions) for
the distros and admins that want these specific, decades-old,
well-established tweaks to how links work? Other LSMs handle policy
via these hooks, and Yama is just doing the same thing.

Thanks,

-Kees

-- 
Kees Cook
ChromeOS Security
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