linux-kernel - Re: [PATCH] perfcounters: allow sysadmin to restrict non-root counting of kernel events

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Date:	Wed, 18 Feb 2009 13:07:20 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perfcounters: allow sysadmin to restrict non-root
 counting of kernel events

On Wed, 2009-02-18 at 21:26 +1100, Paul Mackerras wrote:
> Impact: security feature
> 
> This allows the sysadmin to prevent non-root users from counting
> hardware events that occur in kernel or hypervisor mode via a sysfs file:
> 
> 	/sys/devices/system/cpu/perf_counters/restrict_kernel_events
> 
> This defaults to off (0), allowing users to count kernel and hypervisor
> events, but if the sysadmin writes 1 to that file, any new counters
> created by non-root users will automatically be set to ignore kernel
> and hypervisor events.
> 
> This could be useful if there is a concern that allowing non-root users
> to count kernel or hypervisor events might leak sensitive information.

I would expect it the other way around, don't allow users access to
kernel/hv events unless explicitly granted.

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