From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, eranian@google.com,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 1/2] Fix perf LBR filtering
Date: Thu, 25 Apr 2013 18:48:37 +0200 [thread overview]
Message-ID: <20130425164837.GD5828@dyad.programming.kicks-ass.net> (raw)
In-Reply-To: <20130425164100.GC16732@two.firstfloor.org>
On Thu, Apr 25, 2013 at 06:41:00PM +0200, Andi Kleen wrote:
> > So why not do the same as we do for userspace? Copy MAX_INSN_SIZE bytes
> > and trap -EFAULT.
>
> Read the whole description, then you'll know why that is insecure.
You didn't actually explicitly mention it; you just said unconditional reading
of random addresses was bad.
You list:
> But that is dangerous if can be controlled by the user:
> - It can be used to crash the kernel
> - It allows to probe any physical address for a small set of values
> (valid call op codes) which is an information leak.
> - It may point to a side effect on read MMIO region
Traping the read deals with the first. The second shouldn't be a problem since
we generally only allow kernel info for CAP_ADMIN; if we don't already for LBR
that needs to be fixed separately.
That only leaves the third.. can we descern MMIO maps from the kernel page tables?
next prev parent reply other threads:[~2013-04-25 16:49 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-24 23:04 [PATCH 1/2] Fix perf LBR filtering Andi Kleen
2013-04-24 23:04 ` [PATCH 2/2] perf, x86: Don't allow unusual PEBS raw flags Andi Kleen
2013-04-29 22:16 ` Stephane Eranian
2013-04-29 22:34 ` Andi Kleen
2013-04-29 23:05 ` Stephane Eranian
2013-05-02 7:37 ` Peter Zijlstra
2013-05-06 17:44 ` Stephane Eranian
2013-05-06 18:52 ` Peter Zijlstra
2013-05-06 22:43 ` Stephane Eranian
2013-05-07 6:48 ` Ingo Molnar
2013-05-07 8:48 ` Peter Zijlstra
2013-05-07 11:04 ` Ingo Molnar
2013-05-07 8:43 ` Peter Zijlstra
2013-04-24 23:20 ` [PATCH 1/2] Fix perf LBR filtering Ben Hutchings
2013-04-24 23:24 ` Greg KH
2013-04-25 16:25 ` Peter Zijlstra
2013-04-25 16:41 ` Andi Kleen
2013-04-25 16:48 ` Peter Zijlstra [this message]
2013-04-25 17:00 ` Andi Kleen
2013-04-25 17:18 ` Peter Zijlstra
2013-04-25 17:42 ` Andi Kleen
2013-04-26 7:56 ` Peter Zijlstra
2013-04-26 19:46 ` Andi Kleen
2013-05-01 11:51 ` Ingo Molnar
2013-05-01 11:55 ` Ingo Molnar
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