Subject: [PATCH 5.2 124/215] perf session: Fix potential NULL pointer dereference found by the smatch tool

From: Greg Kroah-Hartman <[email-masked]>
Date: Mon, 29 Jul 2019 21:22:00 +0200

[ Upstream commit f3c8d90757724982e5f07cd77d315eb64ca145ac ]

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 <[email-masked]>
Acked-by: Jiri Olsa <[email-masked]>
Cc: Adrian Hunter <[email-masked]>
Cc: Alexander Shishkin <[email-masked]>
Cc: Alexey Budankov <[email-masked]>
Cc: Alexios Zavras <[email-masked]>
Cc: Andi Kleen <[email-masked]>
Cc: Changbin Du <[email-masked]>
Cc: David S. Miller <[email-masked]>
Cc: Davidlohr Bueso <[email-masked]>
Cc: Eric Saint-Etienne <[email-masked]>
Cc: Jin Yao <[email-masked]>
Cc: Konstantin Khlebnikov <[email-masked]>
Cc: Mathieu Poirier <[email-masked]>
Cc: Namhyung Kim <[email-masked]>
Cc: Peter Zijlstra <[email-masked]>
Cc: Rasmus Villemoes <[email-masked]>
Cc: Song Liu <[email-masked]>
Cc: Suzuki Poulouse <[email-masked]>
Cc: Thomas Gleixner <[email-masked]>
Cc: Thomas Richter <[email-masked]>
Cc: [email-masked]
Link: http://lkml.kernel.org/r/[email-masked]
Signed-off-by: Arnaldo Carvalho de Melo <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 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)
-- 
2.20.1

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