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Message-ID: <20130605130253.GK27176@twins.programming.kicks-ass.net>
Date: Wed, 5 Jun 2013 15:02:53 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: 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 02:38:56PM +0200, Petr Matousek wrote:
> 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)?
There was a leak, notice how Stephane's patch did a
s/PERF_SAMPLE_BRANCH_PERM_PLM/PERF_SAMPLE_BRANCH_KERNEL/ but also places
the check _after_ we propagate the event PLM levels in the case none
were LBR specific.
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