perf record: Fix a segfault in record__read_lost_samples()

When it fails to open events record__open() returns without setting the
session->evlist.  Then it gets a segfault in the function trying to read
lost sample counts.  You can easily reproduce it as a normal user like:

  $ perf record -p 1 true
  ...
  perf: Segmentation fault
  ...

Skip the function if it has no evlist.  And add more protection for evsels
which are not properly initialized.

Fixes: a49aa8a54e861af1 ("perf record: Read and inject LOST_SAMPLES events")
Signed-off-by: Namhyung Kim <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Acked-by: Leo Yan <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 741e763436ca..f4f1619199e5 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1888,6 +1888,10 @@ static void record__read_lost_samples(struct record *rec)
 	struct perf_record_lost_samples *lost;
 	struct evsel *evsel;
 
+	/* there was an error during record__open */
+	if (session->evlist == NULL)
+		return;
+
 	lost = zalloc(PERF_SAMPLE_MAX_SIZE);
 	if (lost == NULL) {
 		pr_debug("Memory allocation failed\n");
@@ -1899,6 +1903,8 @@ static void record__read_lost_samples(struct record *rec)
 	evlist__for_each_entry(session->evlist, evsel) {
 		struct xyarray *xy = evsel->core.sample_id;
 
+		if (xy == NULL || evsel->core.fd == NULL)
+			continue;
 		if (xyarray__max_x(evsel->core.fd) != xyarray__max_x(xy) ||
 		    xyarray__max_y(evsel->core.fd) != xyarray__max_y(xy)) {
 			pr_debug("Unmatched FD vs. sample ID: skip reading LOST count\n");