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

[Leo Yan]

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....@linaro.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