Re: [PATCH v1 1/2] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Leo Yan <leo.yan@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	linux-kernel@vger.kernel.org, Namhyung Kim <namhyung@kernel.org>,
	Robert Walker <robert.walker@arm.com>,
	Jiri Olsa <jolsa@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH v1 1/2] perf cs-etm: Always allocate memory for cs_etm_queue::prev_packet
Date: Mon, 29 Apr 2019 21:07:42 -0400	[thread overview]
Message-ID: <20190430010742.GD7857@kernel.org> (raw)
In-Reply-To: <20190428083228.20246-1-leo.yan@linaro.org>

Em Sun, Apr 28, 2019 at 04:32:27PM +0800, Leo Yan escreveu:
> Robert Walker reported a segmentation fault is observed when process
> CoreSight trace data; this issue can be easily reproduced by the
> command 'perf report --itrace=i1000i' for decoding tracing data.
> 
> If neither the 'b' flag (synthesize branches events) nor 'l' flag
> (synthesize last branch entries) are specified to option '--itrace',
> cs_etm_queue::prev_packet will not been initialised.  After merging
> the code to support exception packets and sample flags, there
> introduced a number of uses of cs_etm_queue::prev_packet without
> checking whether it is valid, for these cases any accessing to
> uninitialised prev_packet will cause crash.
> 
> As cs_etm_queue::prev_packet is used more widely now and it's already
> hard to follow which functions have been called in a context where the
> validity of cs_etm_queue::prev_packet has been checked, this patch
> always allocates memory for cs_etm_queue::prev_packet.
> 
> Reported-by: Robert Walker <robert.walker@arm.com>
> Suggested-by: Robert Walker <robert.walker@arm.com>
> Fixes: 7100b12cf474 ("perf cs-etm: Generate branch sample for exception packet")

Thanks, applied both to perf/urgent, testing them now in the containers.

- Arnaldo

> Fixes: 24fff5eb2b93 ("perf cs-etm: Avoid stale branch samples when flush packet")
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>  tools/perf/util/cs-etm.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 110804936fc3..054b480aab04 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -422,11 +422,9 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
>  	if (!etmq->packet)
>  		goto out_free;
>  
> -	if (etm->synth_opts.last_branch || etm->sample_branches) {
> -		etmq->prev_packet = zalloc(szp);
> -		if (!etmq->prev_packet)
> -			goto out_free;
> -	}
> +	etmq->prev_packet = zalloc(szp);
> +	if (!etmq->prev_packet)
> +		goto out_free;
>  
>  	if (etm->synth_opts.last_branch) {
>  		size_t sz = sizeof(struct branch_stack);
> -- 
> 2.17.1

-- 

- Arnaldo

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