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From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: Wei Li <liwei391@huawei.com>
Cc: Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
	linux-kernel@vger.kernel.org, xiezhipeng1@huawei.com
Subject: Re: [PATCH v2] fix use-after-free in perf_sched__lat
Date: Wed, 22 May 2019 08:08:23 -0300	[thread overview]
Message-ID: <20190522110823.GR8945@kernel.org> (raw)
In-Reply-To: <20190522065555.GA206606@google.com>

Em Wed, May 22, 2019 at 03:56:10PM +0900, Namhyung Kim escreveu:
> On Wed, May 08, 2019 at 10:36:48PM +0800, Wei Li wrote:
> > After thread is added to machine->threads[i].dead in
> > __machine__remove_thread, the machine->threads[i].dead is freed
> > when calling free(session) in perf_session__delete(). So it get a
> > Segmentation fault when accessing it in thread__put().
> > 
> > In this patch, we delay the perf_session__delete until all threads
> > have been deleted.
> > 
> > This can be reproduced by following steps:
> > 	ulimit -c unlimited
> > 	export MALLOC_MMAP_THRESHOLD_=0
> > 	perf sched record sleep 10
> > 	perf sched latency --sort max
> > 	Segmentation fault (core dumped)
> > 
> > Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
> > Signed-off-by: Wei Li <liwei391@huawei.com>
> 
> Acked-by: Namhyung Kim <namhyung@kernel.org>

I'll try to analyse this one soon, but my first impression was that we
should just grab reference counts when keeping a pointer to those
threads instead of keeping _all_ threads alive when supposedly we could
trow away unreferenced data structures.

But this is just a first impression from just reading the patch
description, probably I'm missing something.

Thanks for providing instructions on readily triggering the segfault.

- Arnaldo

  reply	other threads:[~2019-05-22 11:08 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-08 14:36 [PATCH v2] fix use-after-free in perf_sched__lat Wei Li
2019-05-22  6:56 ` Namhyung Kim
2019-05-22 11:08   ` Arnaldo Carvalho de Melo [this message]
2019-05-23  2:50     ` Namhyung Kim
2019-07-04 11:21       ` liwei (GF)
2019-07-04 19:43         ` Arnaldo Carvalho de Melo
2019-07-09 11:29           ` [tip:perf/core] perf thread: Allow references to thread objects after machine__exit() tip-bot for Arnaldo Carvalho de Melo

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