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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	"davej@codemonkey.org.uk" <davej@codemonkey.org.uk>,
	"dvyukov@google.com" <dvyukov@google.com>,
	Stephane Eranian <eranian@gmail.com>
Subject: Re: perf: fuzzer KASAN unwind_get_return_address
Date: Thu, 17 Nov 2016 09:18:48 -0600	[thread overview]
Message-ID: <20161117151848.7sdss3g4waanxfsk@treble> (raw)
In-Reply-To: <20161117090446.GC3142@twins.programming.kicks-ass.net>

On Thu, Nov 17, 2016 at 10:04:46AM +0100, Peter Zijlstra wrote:
> On Wed, Nov 16, 2016 at 10:48:28PM -0600, Josh Poimboeuf wrote:
> > Peter or Vince, can you try to recreate with this patch?  It dumps the
> > raw stack contents during a stack dump.  Hopefully that would give a
> > clue about what's going wrong.
> 
> 
> Here goes... I'll do another run and get you the results of that as
> well.

Thanks, I just waded through this and it turned up some good clues.  And
according to 'git blame', you might be able to help :-)

It's not stack corruption.  Instead it looks like
__intel_pmu_pebs_event() is creating a bad or stale pt_regs which gets
passed to the unwinder.  Specifically, regs->bp points to a seemingly
random address on the NMI stack.  Which seems odd, considering the code
itself is running on the same NMI stack.

I don't know much about the PEBS code but it seems like it's passing
some stale data.  Either that or there's some NMI nesting going on.

-- 
Josh

  parent reply	other threads:[~2016-11-17 17:44 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-15 17:43 perf: fuzzer KASAN unwind_get_return_address Vince Weaver
2016-11-15 18:57 ` Peter Zijlstra
2016-11-15 19:04   ` Dmitry Vyukov
2016-11-15 20:56     ` Josh Poimboeuf
2016-11-15 19:05   ` Vince Weaver
2016-11-15 20:57     ` Josh Poimboeuf
2016-11-16 13:03       ` Peter Zijlstra
2016-11-16 13:18         ` Dmitry Vyukov
2016-11-16 14:37         ` Josh Poimboeuf
2016-11-16 14:49           ` Peter Zijlstra
2016-11-16 14:58             ` Josh Poimboeuf
2016-11-16 14:58             ` Peter Zijlstra
2016-11-17  4:48               ` Josh Poimboeuf
2016-11-17  9:04                 ` Peter Zijlstra
2016-11-17  9:13                   ` Peter Zijlstra
2016-11-17  9:30                     ` Peter Zijlstra
2016-11-17  9:48                       ` Dmitry Vyukov
2016-11-17 14:01                         ` Josh Poimboeuf
2016-11-17 14:25                           ` Vince Weaver
2016-11-17 14:36                             ` Josh Poimboeuf
2016-11-17 14:58                               ` Dmitry Vyukov
2016-11-17 17:15                                 ` Vince Weaver
2016-11-17 15:18                   ` Josh Poimboeuf [this message]
2016-11-17 16:07                     ` Peter Zijlstra
2016-11-17 17:17                       ` Peter Zijlstra
2016-11-22 12:30                         ` [tip:perf/urgent] perf/x86/intel: Cure bogus unwind from PEBS entries tip-bot for Peter Zijlstra
2016-11-16 15:06             ` perf: fuzzer KASAN unwind_get_return_address Vince Weaver
2016-11-17 15:57         ` [PATCH 1/2] unwind: prevent KASAN false positive warnings in guess unwinder Josh Poimboeuf
2016-11-17 15:57           ` [PATCH 2/2] dumpstack: prevent KASAN false positive warnings Josh Poimboeuf
2016-11-18  9:04             ` [tip:x86/urgent] x86/dumpstack: Prevent " tip-bot for Josh Poimboeuf
2016-11-17 20:26           ` [PATCH 1/2] unwind: prevent KASAN false positive warnings in guess unwinder Josh Poimboeuf
2016-11-18  8:38             ` Ingo Molnar
2016-11-18  9:04           ` [tip:x86/urgent] x86/unwind: Prevent " tip-bot for Josh Poimboeuf

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