linux-kernel - Re: [PATCH v4] kptr_restrict for hiding kernel pointers

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Message-ID: <20101222130349.GB13412@elte.hu>
Date:	Wed, 22 Dec 2010 14:03:49 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Dan Rosenberg <drosenberg@...curity.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org, jmorris@...ei.org,
	eric.dumazet@...il.com, tgraf@...radead.org, eugeneteo@...nel.org,
	kees.cook@...onical.com, davem@...emloft.net,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	eparis@...isplace.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v4] kptr_restrict for hiding kernel pointers


* Dan Rosenberg <drosenberg@...curity.com> wrote:

> +kptr_restrict:
> +
> +This toggle indicates whether restrictions are placed on
> +exposing kernel addresses via /proc and other interfaces.  When
> +kptr_restrict is set to (0), the default, there are no
> +restrictions.  When kptr_restrict is set to (1), kernel pointers
> +printed using the %pK format specifier will be replaced with 0's
> +unless the user has CAP_SYSLOG.  When kptr_restrict is set to
> +(2), kernel pointers printed using %pK will be replaced with 0's
> +regardless of privileges.

Hm, why is it off by default? Is there some user-space regression that is caused by 
this?

We really want good security measures to be active by default (and to work by 
default) - they are not worth much if they are not.

Thanks,

	Ingo
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