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From: "Jin, Yao" <yao.jin@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: acme@kernel.org, jolsa@kernel.org, mingo@redhat.com,
	alexander.shishkin@linux.intel.com, me@kylehuey.com,
	Linux-kernel@vger.kernel.org, vincent.weaver@maine.edu,
	will.deacon@arm.com, eranian@google.com, namhyung@kernel.org,
	ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com
Subject: Re: [PATCH v1 0/2] perf: Drop leaked kernel samples
Date: Fri, 15 Jun 2018 16:01:45 +0800	[thread overview]
Message-ID: <11958be5-dc05-611b-6839-f1f6903c7ca8@linux.intel.com> (raw)
In-Reply-To: <20180615074504.GA2458@hirez.programming.kicks-ass.net>



On 6/15/2018 3:45 PM, Peter Zijlstra wrote:
> On Fri, Jun 15, 2018 at 06:03:21PM +0800, Jin Yao wrote:
>> On workloads that do a lot of kernel entry/exits we see kernel
>> samples, even though :u is specified. This is due to skid existing.
>>
>> This might be a security issue because it can leak kernel addresses even
>> though kernel sampling support is disabled.
>>
>> One patch "perf/core: Drop kernel samples even though :u is specified"
>> was posted in last year but it was reverted because it introduced a
>> regression issue that broke the rr-project.
>>
>> Now this patch set uses sysctl to control the dropping of leaked
>> kernel samples.
> 
> So what happened to the suggestion of keeping the samples but 0-stuffing
> all the tricky bits?
> 

Bring more overhead to kernel if we zero the bits considering the number 
of leaked samples may be not too small?

And the skid information may be interesting (see example of hitting on 
page_fault in previous mail). If we zero it, we will not know.

Thanks
Jin Yao

  reply	other threads:[~2018-06-15  8:01 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-15 10:03 [PATCH v1 0/2] perf: Drop leaked kernel samples Jin Yao
2018-06-15  3:35 ` Kyle Huey
2018-06-15  5:11   ` Jin, Yao
2018-06-15 17:16     ` Kyle Huey
2018-06-15 17:34       ` Robert O'Callahan
2018-06-16  0:50         ` Jin, Yao
2018-06-16  0:56           ` Kyle Huey
2018-06-16  1:18             ` Jin, Yao
2018-06-15  7:45 ` Peter Zijlstra
2018-06-15  8:01   ` Jin, Yao [this message]
2018-06-15  8:12     ` Peter Zijlstra
2018-06-15  8:24       ` Jin, Yao
2018-06-15 16:54       ` Stephane Eranian
2018-06-15 10:03 ` [PATCH v1 1/2] perf/core: Use sysctl to turn on/off dropping " Jin Yao
2018-06-15  5:59   ` Stephane Eranian
2018-06-15  7:15     ` Jin, Yao
2018-06-19 16:50       ` Stephane Eranian
2018-06-15  6:02   ` Stephane Eranian
2018-06-15  8:16     ` Peter Zijlstra
2018-06-15 13:31       ` Liang, Kan
2018-06-18 10:41         ` Peter Zijlstra
2018-06-15 11:36   ` Mark Rutland
2018-06-16  1:27     ` Linus Torvalds
2018-06-18 10:51       ` Peter Zijlstra
2018-06-18  6:55     ` Jin, Yao
2018-06-18 10:45       ` Peter Zijlstra
2018-06-19  1:39         ` Jin, Yao
2018-06-19  6:01           ` Mark Rutland
2018-06-15 10:03 ` [PATCH v1 2/2] perf Documentation: Introduce the sysctl perf_allow_sample_leakage Jin Yao

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