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Date: Wed, 5 Jun 2013 14:38:56 +0200
From: Petr Matousek <pmatouse@...hat.com>
To: a.p.zijlstra@...llo.nl
Cc: eranian@...gle.com, ak@...ux.intel.com, security@...nel.org,
        Marcus Meissner <meissner@...e.de>, oss-security@...ts.openwall.com
Subject: Re: CVE Request: More perf security fixes

On Wed, Jun 05, 2013 at 02:15:59PM +0200, Peter Zijlstra wrote:
> On Wed, Jun 05, 2013 at 02:10:54PM +0200, Petr Matousek wrote:
> > Hello, Peter.
> > 
> > On Tue, Jun 04, 2013 at 05:53:16PM +0200, Marcus Meissner wrote:
> > > 1. Info leak (?) via PERF_SAMPLE_BRANCH_KERNEL
> > > 
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7cc23cd6c0c7d7f4bee057607e7ce01568925717
> > > 
> > > commit 7cc23cd6c0c7d7f4bee057607e7ce01568925717
> > > Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > > Date:   Fri May 3 14:11:25 2013 +0200
> > > 
> > >     perf/x86/intel/lbr: Demand proper privileges for PERF_SAMPLE_BRANCH_KERNEL
> > > 
> > >     We should always have proper privileges when requesting kernel
> > >     data.
> > > 
> > >     Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > >     Cc: <stable@...nel.org>
> > >     Cc: Andi Kleen <ak@...ux.intel.com>
> > >     Cc: eranian@...gle.com
> > >     Link: http://lkml.kernel.org/r/20130503121256.230745028@chello.nl
> > >     [ Fix build error reported by fengguang.wu@...el.com, propagate error code back. ]
> > >     Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > >     Link: http://lkml.kernel.org/n/tip-v0x9ky3ahzr6nm3c6ilwrili@git.kernel.org
> > 
> > There is similar check in perf_copy_attr() which is called from
> > perf_event_open syscall --
> > 
> >                 /* kernel level capture: check permissions */
> >                 if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
> >                     && perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> >                         return -EACCES;
> > 
> > It seems to me that it covers PERF_SAMPLE_BRANCH_KERNEL as well. Am I
> > missing something?
> > 
> 
> I overlooked it, also its slightly broken. See the discussion at: 
>   https://lkml.org/lkml/2013/5/21/166

Got it, thanks for the pointer. So it is safe to say there never was a
leak in this case (and thus no security issue worth CVE)?

Thanks,
-- 
Petr Matousek / Red Hat Security Response Team

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