Date: Sun, 7 Nov 2010 10:08:05 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Willy Tarreau <w@1wt.eu>
Cc: Marcus Meissner <meissner@suse.de>, security@kernel.org, mort@sgi.com,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, fweisbec@gmail.com,
        "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        jason.wessel@windriver.com, tj@kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [Security] [PATCH] kernel: make /proc/kallsyms mode 400 to
 reduce ease of attacking
Message-ID: <20101107090805.GA27983@elte.hu>
References: <20101104114648.GA23381@elte.hu>
 <20101104122906.GH25118@suse.de>
 <20101104135802.GA31416@elte.hu>
 <20101104141104.GA31753@elte.hu>
 <20101104143322.GL25118@suse.de>
 <20101104190804.GA16099@elte.hu>
 <20101104212920.GA31256@1wt.eu>
 <20101104215157.GA25128@elte.hu>
 <20101104223526.GC31236@1wt.eu>
 <20101107085016.GA23843@elte.hu>
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* Ingo Molnar <mingo@elte.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@aldebaran ~]# 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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