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Date:   Wed, 22 May 2019 15:56:10 +0900
From:   Namhyung Kim <namhyung@kernel.org>
To:     Wei Li <liwei391@huawei.com>
Cc:     acme@kernel.org, jolsa@redhat.com,
        alexander.shishkin@linux.intel.com, peterz@infradead.org,
        mingo@redhat.com, linux-kernel@vger.kernel.org,
        xiezhipeng1@huawei.com
Subject: Re: [PATCH v2] fix use-after-free in perf_sched__lat
Message-ID: <20190522065555.GA206606@google.com>
References: <20190508143648.8153-1-liwei391@huawei.com>
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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>

Thahks,
Namhyung


> ---
>  tools/perf/builtin-sched.c | 63 ++++++++++++++++++++++++++------------
>  1 file changed, 43 insertions(+), 20 deletions(-)
> 
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 275f2d92a7bf..8a4841fa124c 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -1774,7 +1774,8 @@ static int perf_sched__process_comm(struct perf_tool *tool __maybe_unused,
>  	return 0;
>  }
>  
> -static int perf_sched__read_events(struct perf_sched *sched)
> +static int __perf_sched__read_events(struct perf_sched *sched,
> +					struct perf_session *session)
>  {
>  	const struct perf_evsel_str_handler handlers[] = {
>  		{ "sched:sched_switch",	      process_sched_switch_event, },
> @@ -1783,30 +1784,17 @@ static int perf_sched__read_events(struct perf_sched *sched)
>  		{ "sched:sched_wakeup_new",   process_sched_wakeup_event, },
>  		{ "sched:sched_migrate_task", process_sched_migrate_task_event, },
>  	};
> -	struct perf_session *session;
> -	struct perf_data data = {
> -		.path  = input_name,
> -		.mode  = PERF_DATA_MODE_READ,
> -		.force = sched->force,
> -	};
> -	int rc = -1;
> -
> -	session = perf_session__new(&data, false, &sched->tool);
> -	if (session == NULL) {
> -		pr_debug("No Memory for session\n");
> -		return -1;
> -	}
>  
>  	symbol__init(&session->header.env);
>  
>  	if (perf_session__set_tracepoints_handlers(session, handlers))
> -		goto out_delete;
> +		return -1;
>  
>  	if (perf_session__has_traces(session, "record -R")) {
>  		int err = perf_session__process_events(session);
>  		if (err) {
>  			pr_err("Failed to process events, error %d", err);
> -			goto out_delete;
> +			return -1;
>  		}
>  
>  		sched->nr_events      = session->evlist->stats.nr_events[0];
> @@ -1814,9 +1802,28 @@ static int perf_sched__read_events(struct perf_sched *sched)
>  		sched->nr_lost_chunks = session->evlist->stats.nr_events[PERF_RECORD_LOST];
>  	}
>  
> -	rc = 0;
> -out_delete:
> +	return 0;
> +}
> +
> +static int perf_sched__read_events(struct perf_sched *sched)
> +{
> +	struct perf_session *session;
> +	struct perf_data data = {
> +		.path  = input_name,
> +		.mode  = PERF_DATA_MODE_READ,
> +		.force = sched->force,
> +	};
> +	int rc;
> +
> +	session = perf_session__new(&data, false, &sched->tool);
> +	if (session == NULL) {
> +		pr_debug("No Memory for session\n");
> +		return -1;
> +	}
> +
> +	rc = __perf_sched__read_events(sched, session);
>  	perf_session__delete(session);
> +
>  	return rc;
>  }
>  
> @@ -3130,12 +3137,25 @@ static void perf_sched__merge_lat(struct perf_sched *sched)
>  
>  static int perf_sched__lat(struct perf_sched *sched)
>  {
> +	struct perf_session *session;
> +	struct perf_data data = {
> +		.path  = input_name,
> +		.mode  = PERF_DATA_MODE_READ,
> +		.force = sched->force,
> +	};
>  	struct rb_node *next;
> +	int rc = -1;
>  
>  	setup_pager();
>  
> -	if (perf_sched__read_events(sched))
> +	session = perf_session__new(&data, false, &sched->tool);
> +	if (session == NULL) {
> +		pr_debug("No Memory for session\n");
>  		return -1;
> +	}
> +
> +	if (__perf_sched__read_events(sched, session))
> +		goto out_delete;
>  
>  	perf_sched__merge_lat(sched);
>  	perf_sched__sort_lat(sched);
> @@ -3164,7 +3184,10 @@ static int perf_sched__lat(struct perf_sched *sched)
>  	print_bad_events(sched);
>  	printf("\n");
>  
> -	return 0;
> +	rc = 0;
> +out_delete:
> +	perf_session__delete(session);
> +	return rc;
>  }
>  
>  static int setup_map_cpus(struct perf_sched *sched)
> -- 
> 2.17.1
>