Patch "perf inject: Copy events when reordering events in pipe mode" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

perf inject: Copy events when reordering events in pipe mode

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-inject-copy-events-when-reordering-events-in-pipe-mode.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: David Carrillo-Cisneros <[email protected]>
Date: Mon, 10 Apr 2017 13:14:27 -0700
Subject: perf inject: Copy events when reordering events in pipe mode

From: David Carrillo-Cisneros <[email protected]>

[ Upstream commit 1e0d4f0200e4dbdfc38d818f329d8a0955f7c6f5 ]

__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

Committer testing:

Before:

  $ perf record -o - stress -t 2 -c 2 | perf inject -b > /dev/null
  stress: info: [8297] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
  stress: info: [8297] successful run completed in 2s
  [ perf record: Woken up 3 times to write data ]
  [ perf record: Captured and wrote 0.000 MB - ]
  Warning:
  Found 1 unknown events!

Is this an older tool processing a perf.data file generated by a more recent tool?

If that is not the case, consider reporting to [email protected].

$

After:

  $ perf record -o - stress -t 2 -c 2 | perf inject -b > /dev/null
  stress: info: [9027] dispatching hogs: 2 cpu, 0 io, 0 vm, 0 hdd
  stress: info: [9027] successful run completed in 2s
  [ perf record: Woken up 3 times to write data ]
  [ perf record: Captured and wrote 0.000 MB - ]
  no symbols found in /usr/bin/stress, maybe install a debug package?
  no symbols found in /usr/bin/stress, maybe install a debug package?
  $

---
 tools/perf/util/ordered-events.c |    3 ++-
 tools/perf/util/session.c        |    1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

@@ -79,7 +79,7 @@ static union perf_event *dup_event(struc
 
 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 order
 	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,

@@ -1628,6 +1628,7 @@ static int __perf_session__process_pipe_
 	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));

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/perf-session-don-t-rely-on-evlist-in-pipe-mode.patch queue-4.9/perf-inject-copy-events-when-reordering-events-in-pipe-mode.patch queue-4.9/perf-stat-fix-bug-in-handling-events-in-error-state.patch