linux-kernel - Re: [Security] [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking

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Date:	Sun, 7 Nov 2010 13:37:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Willy Tarreau <w@....eu>
Cc:	Marcus Meissner <meissner@...e.de>, security@...nel.org,
	mort@....com, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	fweisbec@...il.com, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org, jason.wessel@...driver.com,
	tj@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Security] [PATCH] kernel: make /proc/kallsyms mode 400 to
 reduce ease of attacking

* Willy Tarreau <w@....eu> wrote:

> > All must be closed down for unprivileged user-space, for this to be effective, 
> > obviously.
> 
> This would only be effective against finding a precise version. [...]

I'm glad that you agree with my point.

> [...] There's no need for that, what you want is to hide kernel pointers, [...]

That's a new claim from you - and when put like that it's wrong too: if the goal is 
to introduce risk of detection to attackers (which i suggested to be an efficient 
security measure), then hiding/fuzzing version information is an essential/needed 
piece of such a measure, not something for which there is 'no need'.

Hiding the address of kernel data/code structures is another piece of such a larger 
goal. Btw., as i argued it to Marcus already, hiding /proc/kallsyms will not hide 
these addresses on the vast majority of Linux systems, and that the patch would only 
cure the symptom, not the cause:

 |
 | But without actually declaring and achieving that sandboxing goal this security 
 | measure is just a feel-good thing really [...]
 |

Anyway, i wasnt particularly successful in conveying my past arguments to you so i'd 
rather leave the discussion at this point. You made your points and i made my points 
as well.

Thanks,

	Ingo
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