[PATCH perf/urgent] perf tools: Fix crash in ordered_events__free

[Jiri Olsa]

Song Liu reported crash in perf record:

> #0  0x0000000000500055 in ordered_events(float, long double,...)(...) ()
> #1  0x0000000000500196 in ordered_events.reinit ()
> #2  0x00000000004fe413 in perf_session.process_events ()
> #3  0x0000000000440431 in cmd_record ()
> #4  0x00000000004a439f in run_builtin ()
> #5  0x000000000042b3e5 in main ()"

This can happen when we get out of the buffers during
event processing. The subsequent ordered_events__free
assumes the oe->buffer != NULL and crashes. Adding
the check to prevent that.

Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Fixes: d5ceb62b3654 ("perf ordered_events: Add 'struct ordered_events_buffer' layer")
Reported-by: Song Liu <liu.song.a23@xxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-914bml5kabz2m9mbywd7el9l@xxxxxxxxxxxxxx
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/util/ordered-events.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index 897589507d97..ea523d3b248f 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -391,8 +391,10 @@ void ordered_events__free(struct ordered_events *oe)
 	 * Current buffer might not have all the events allocated
 	 * yet, we need to free only allocated ones ...
 	 */
-	list_del(&oe->buffer->list);
-	ordered_events_buffer__free(oe->buffer, oe->buffer_idx, oe);
+	if (oe->buffer) {
+		list_del(&oe->buffer->list);
+		ordered_events_buffer__free(oe->buffer, oe->buffer_idx, oe);
+	}
 
 	/* ... and continue with the rest */
 	list_for_each_entry_safe(buffer, tmp, &oe->to_free, list) {
-- 
2.17.2