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 10:08:05 +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


* Ingo Molnar <mingo@...e.hu> wrote:

> If your claim that 'kernel version is needed at many places' is true then why am i 
> seeing this on a pretty general distro box bootup:
> 
>  [root@...ebaran ~]# uname -a
>  Linux aldebaran 2.6.99-tip-01574-g6ba54c9-dirty #1 SMP Sun Nov 7 10:24:38 CET 2010 x86_64 x86_64 x86_64 GNU/Linux
> 
> ?
> 
> Yes, some user-space might be unhappy if we set the version _back_ to say 2.4.0, 
> but we could (as the patch below) fuzz up the version information from 
> unprivileged attackers easily.

Btw., with an 'exploit honeypot' and 'version fuzzing' the uname output would look 
like this to an unprivileged user:

  $ uname -a
  Linux aldebaran 2.6.99 x86_64 x86_64 x86_64 GNU/Linux

[ we wouldnt want to include the date or the SHA1 of the kernel, obviously. ]

And it would look like this to root:

  # uname -a
  Linux aldebaran 2.6.37-tip-01574-g6ba54c9-dirty #1 SMP Sun Nov 7 10:24:38 CET 2010 x86_64 x86_64 x86_64 GNU/Linux

	Ingo
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