[PATCH 4.16 185/272] perf/core: Fix perf_output_read_group()

Greg Kroah-Hartman
2018-05-28T11:35:14Z

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 9e5b127d6f33468143d90c8a45ca12410e4c3fa7 ]

Mark reported his arm64 perf fuzzer runs sometimes splat like:

armv8pmu_read_counter+0x1e8/0x2d8
armpmu_event_update+0x8c/0x188
armpmu_read+0xc/0x18
perf_output_read+0x550/0x11e8
perf_event_read_event+0x1d0/0x248
perf_event_exit_task+0x468/0xbb8
do_exit+0x690/0x1310
do_group_exit+0xd0/0x2b0
get_signal+0x2e8/0x17a8
do_signal+0x144/0x4f8
do_notify_resume+0x148/0x1e8
work_pending+0x8/0x14

which asserts that we only call pmu::read() on ACTIVE events.

The above callchain does:

perf_event_exit_task()
perf_event_exit_task_context()
task_ctx_sched_out() // INACTIVE
perf_event_exit_event()
perf_event_set_state(EXIT) // EXIT
sync_child_event()
perf_event_read_event()
perf_output_read()
perf_output_read_group()
leader->pmu->read()

Which results in doing a pmu::read() on an !ACTIVE event.

I _think_ this is 'new' since we added attr.inherit_stat, which added
the perf_event_read_event() to the exit path, without that
perf_event_read_output() would only trigger from samples and for
@event to trigger a sample, it's leader _must_ be ACTIVE too.

Still, adding this check makes it consistent with the @sub case for
the siblings.

Reported-and-Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/events/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5770,7 +5770,8 @@ static void perf_output_read_group(struc
if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
values[n++] = running;

- if (leader != event)
+ if ((leader != event) &&
+ (leader->state == PERF_EVENT_STATE_ACTIVE))
leader->pmu->read(leader);

values[n++] = perf_event_count(leader);