linux-kernel - Re: [PATCH] kernel/time: Make /proc/timer

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Message-Id: <20101117123039.d975aa70.akpm@linux-foundation.org>
Date:	Wed, 17 Nov 2010 12:30:39 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Marcus Meissner <meissner@...e.de>, tglx@...utronix.de,
	mingo@...e.hu, rusty@...tcorp.com.au,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/time: Make /proc/timer_list mode 0400

On Wed, 17 Nov 2010 18:18:32 +0100
Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> On Wed, 2010-11-17 at 18:08 +0100, Marcus Meissner wrote:
> > Hi,
> > 
> > /proc/timer_list contains kernel addresses, like e.g.:
> >  #0: <c000000001404158>, tick_sched_timer, S:01, .tick_nohz_restart_sched_tick, swapper/0
> >  ...
> > 
> > Avoid leaking them to user space to make writing kernel exploits a bit harder.
> > 
> > (I currently cannot think of a userland tool that uses this, this is
> > likely pretty much root-only.)
> 
> iirc powertop parses this..

I bet it doesn't look at the kernel address (why was that added in the
first place, anyway?)

I'd suggest that the risk of breakage would be much less if we left the
file permissions alone and arranged for those addresses to be
0000000000000000 for non-root readers.
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