linux-kernel - [PATCH v1 08/11] perf session: Smatch: Fix potential NULL pointer dereference

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Date:   Tue,  2 Jul 2019 18:34:17 +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 08/11] perf session: Smatch: Fix potential NULL pointer dereference

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

  tools/perf/util/session.c:1252
  dump_read() error: we previously assumed 'evsel' could be null
  (see line 1249)

tools/perf/util/session.c
1240 static void dump_read(struct perf_evsel *evsel, union perf_event *event)
1241 {
1242         struct read_event *read_event = &event->read;
1243         u64 read_format;
1244
1245         if (!dump_trace)
1246                 return;
1247
1248         printf(": %d %d %s %" PRIu64 "\n", event->read.pid, event->read.tid,
1249                evsel ? perf_evsel__name(evsel) : "FAIL",
1250                event->read.value);
1251
1252         read_format = evsel->attr.read_format;
                           ^^^^^^^

'evsel' could be NULL pointer, for this case this patch directly bails
out without dumping read_event.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/util/session.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 54cf163347f7..2e61dd6a3574 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1249,6 +1249,9 @@ static void dump_read(struct perf_evsel *evsel, union perf_event *event)
 	       evsel ? perf_evsel__name(evsel) : "FAIL",
 	       event->read.value);
 
+	if (!evsel)
+		return;
+
 	read_format = evsel->attr.read_format;
 
 	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
-- 
2.17.1