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[68.147.8.254]) by smtp.gmail.com with ESMTPSA id k16sm14111163pfa.87.2019.07.02.10.03.08 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 02 Jul 2019 10:03:09 -0700 (PDT) Date: Tue, 2 Jul 2019 11:03:06 -0600 From: Mathieu Poirier To: Leo Yan Cc: Arnaldo Carvalho de Melo , Peter Zijlstra , Ingo Molnar , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Suzuki K Poulose , Andi Kleen , "David S. Miller" , Davidlohr Bueso , Rasmus Villemoes , Jin Yao , Song Liu , Adrian Hunter , Alexios Zavras , Thomas Gleixner , Changbin Du , Eric Saint-Etienne , Konstantin Khlebnikov , Thomas Richter , Alexey Budankov , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v1 11/11] perf cs-etm: Smatch: Fix potential NULL pointer dereference Message-ID: <20190702170306.GA17808@xps15> References: <20190702103420.27540-1-leo.yan@linaro.org> <20190702103420.27540-12-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190702103420.27540-12-leo.yan@linaro.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Leo, On Tue, Jul 02, 2019 at 06:34:20PM +0800, Leo Yan wrote: > Based on the following report from Smatch, fix the potential > NULL pointer dereference check. > > tools/perf/util/cs-etm.c:2545 > cs_etm__process_auxtrace_info() error: we previously assumed > 'session->itrace_synth_opts' could be null (see line 2541) > > tools/perf/util/cs-etm.c > 2541 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > 2542 etm->synth_opts = *session->itrace_synth_opts; > 2543 } else { > 2544 itrace_synth_opts__set_default(&etm->synth_opts, > 2545 session->itrace_synth_opts->default_no_sample); > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > 2546 etm->synth_opts.callchain = false; > 2547 } > > To dismiss the potential NULL pointer dereference, this patch validates > the pointer 'session->itrace_synth_opts' before access its elements. > > Signed-off-by: Leo Yan > --- > tools/perf/util/cs-etm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c > index 0c7776b51045..b79df56eb9df 100644 > --- a/tools/perf/util/cs-etm.c > +++ b/tools/perf/util/cs-etm.c > @@ -2540,7 +2540,7 @@ int cs_etm__process_auxtrace_info(union perf_event *event, > > if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > etm->synth_opts = *session->itrace_synth_opts; > - } else { > + } else if (session->itrace_synth_opts) { This will work but we end up checking session->itrace_synth_opts twice. I suggest to check it once and then process with the if/else if valid: if (session->itrace_synth_opts) { if (session->itrace_synth_opts->set) { ... } else { ... } } Thanks, Mathieu > itrace_synth_opts__set_default(&etm->synth_opts, > session->itrace_synth_opts->default_no_sample); > etm->synth_opts.callchain = false; > -- > 2.17.1 >