linux-kernel - [PATCH v1 10/11] perf intel-pt: Smatch: Fix potential NULL pointer dereference

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Message-Id: <20190702103420.27540-11-leo.yan@linaro.org>
Date:   Tue,  2 Jul 2019 18:34:19 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        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>,
        Andi Kleen <ak@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Davidlohr Bueso <dave@...olabs.net>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Song Liu <songliubraving@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Changbin Du <changbin.du@...el.com>,
        Eric Saint-Etienne <eric.saint.etienne@...cle.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v1 10/11] perf intel-pt: Smatch: Fix potential NULL pointer dereference

Based on the following report from Smatch, fix the potential
NULL pointer dereference check.

  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         }

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 <leo.yan@...aro.org>
---
 tools/perf/util/intel-pt.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 550db6e77968..88b567bdf1f9 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
 
 	if (session->itrace_synth_opts && session->itrace_synth_opts->set) {
 		pt->synth_opts = *session->itrace_synth_opts;
-	} else {
+	} else if (session->itrace_synth_opts) {
 		itrace_synth_opts__set_default(&pt->synth_opts,
 				session->itrace_synth_opts->default_no_sample);
 		if (!session->itrace_synth_opts->default_no_sample &&
@@ -3203,8 +3203,7 @@ 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;
 	}
 
-- 
2.17.1