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

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Message-ID: <alpine.LFD.2.00.1011172137040.2900@localhost6.localdomain6>
Date:	Wed, 17 Nov 2010 21:37:44 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Marcus Meissner <meissner@...e.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, Andrew Morton wrote:

> 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.

You beat me to it. Having the full information is quite helpful at
times.

Thanks,

	tglx

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