linux-kernel - Re: [PATCH v2 3/4] perf intel-pt: Smatch: Fix potential NULL pointer dereference

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Date:   Mon, 8 Jul 2019 18:59:40 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/4] perf intel-pt: Smatch: Fix potential NULL pointer
 dereference

Em Mon, Jul 08, 2019 at 10:39:36PM +0800, Leo Yan escreveu:
> Based on the following report from Smatch, fix the potential
> NULL pointer dereference check.

Adrian, are you ok now with these two for pt and bts? Can I have your
acked-by?

- Arnaldo
 
>   tools/perf/util/intel-pt.c:3200
>   intel_pt_process_auxtrace_info() error: we previously assumed
>   'session->itrace_synth_opts' could be null (see line 3196)
> 
>   tools/perf/util/intel-pt.c:3206
>   intel_pt_process_auxtrace_info() warn: variable dereferenced before
>   check 'session->itrace_synth_opts' (see line 3200)
> 
> tools/perf/util/intel-pt.c
> 3196         if (session->itrace_synth_opts && session->itrace_synth_opts->set) {
> 3197                 pt->synth_opts = *session->itrace_synth_opts;
> 3198         } else {
> 3199                 itrace_synth_opts__set_default(&pt->synth_opts,
> 3200                                 session->itrace_synth_opts->default_no_sample);
>                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
> 3201                 if (!session->itrace_synth_opts->default_no_sample &&
> 3202                     !session->itrace_synth_opts->inject) {
> 3203                         pt->synth_opts.branches = false;
> 3204                         pt->synth_opts.callchain = true;
> 3205                 }
> 3206                 if (session->itrace_synth_opts)
>                          ^^^^^^^^^^^^^^^^^^^^^^^^^^
> 3207                         pt->synth_opts.thread_stack =
> 3208                                 session->itrace_synth_opts->thread_stack;
> 3209         }
> 
> 'session->itrace_synth_opts' is impossible to be a NULL pointer in
> intel_pt_process_auxtrace_info(), thus this patch removes the NULL
> test for 'session->itrace_synth_opts'.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/util/intel-pt.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index c76a96f777fb..df061599fef4 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -3210,7 +3210,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
>  		goto err_delete_thread;
>  	}
>  
> -	if (session->itrace_synth_opts && session->itrace_synth_opts->set) {
> +	if (session->itrace_synth_opts->set) {
>  		pt->synth_opts = *session->itrace_synth_opts;
>  	} else {
>  		itrace_synth_opts__set_default(&pt->synth_opts,
> @@ -3220,8 +3220,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
>  			pt->synth_opts.branches = false;
>  			pt->synth_opts.callchain = true;
>  		}
> -		if (session->itrace_synth_opts)
> -			pt->synth_opts.thread_stack =
> +		pt->synth_opts.thread_stack =
>  				session->itrace_synth_opts->thread_stack;
>  	}
>  
> @@ -3241,11 +3240,9 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
>  		pt->cbr2khz = tsc_freq / pt->max_non_turbo_ratio / 1000;
>  	}
>  
> -	if (session->itrace_synth_opts) {
> -		err = intel_pt_setup_time_ranges(pt, session->itrace_synth_opts);
> -		if (err)
> -			goto err_delete_thread;
> -	}
> +	err = intel_pt_setup_time_ranges(pt, session->itrace_synth_opts);
> +	if (err)
> +		goto err_delete_thread;
>  
>  	if (pt->synth_opts.calls)
>  		pt->branches_filter |= PERF_IP_FLAG_CALL | PERF_IP_FLAG_ASYNC |
> -- 
> 2.17.1

-- 

- Arnaldo