linux-kernel - [PATCH 2/7] perf inject: copy events when reordering events in pipe mode

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Date:   Mon, 10 Apr 2017 13:14:27 -0700
From:   David Carrillo-Cisneros <davidcc@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, Simon Que <sque@...omium.org>,
        Wang Nan <wangnan0@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
        He Kuang <hekuang@...wei.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Paul Turner <pjt@...gle.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>
Subject: [PATCH 2/7] perf inject: copy events when reordering events in pipe mode

__perf_session__process_pipe_events reuses the same memory buffer to
process all events in the pipe.

When reordering is needed (e.g. -b option), events are not immediately
flushed, but kept around until reordering is possible, causing
memory corruption.

The problem is usually observed by a "Unknown sample error" output. It
can easily be reproduced by:

  perf record -o - noploop | perf inject -b > output

Signed-off-by: David Carrillo-Cisneros <davidcc@...gle.com>
---
 tools/perf/util/ordered-events.c | 3 ++-
 tools/perf/util/session.c        | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index fe84df1875aa..e70e935b1841 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -79,7 +79,7 @@ static union perf_event *dup_event(struct ordered_events *oe,
 
 static void free_dup_event(struct ordered_events *oe, union perf_event *event)
 {
-	if (oe->copy_on_queue) {
+	if (event && oe->copy_on_queue) {
 		oe->cur_alloc_size -= event->header.size;
 		free(event);
 	}
@@ -150,6 +150,7 @@ void ordered_events__delete(struct ordered_events *oe, struct ordered_event *eve
 	list_move(&event->list, &oe->cache);
 	oe->nr_events--;
 	free_dup_event(oe, event->event);
+	event->event = NULL;
 }
 
 int ordered_events__queue(struct ordered_events *oe, union perf_event *event,
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 24259bc2c598..a25302bc55a8 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1656,6 +1656,7 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
 	buf = malloc(cur_size);
 	if (!buf)
 		return -errno;
+	ordered_events__set_copy_on_queue(oe, true);
 more:
 	event = buf;
 	err = readn(fd, event, sizeof(struct perf_event_header));
-- 
2.12.2.715.g7642488e1d-goog