perf/aux: Fix AUX output stopping

BugLink: https://bugs.launchpad.net/bugs/1851876
commit f3a519e4add93b7b31a6616f0b09635ff2e6a159 upstream.

Commit:

  8a58ddae2379 ("perf/core: Fix exclusive events' grouping")

allows CAP_EXCLUSIVE events to be grouped with other events. Since all
of those also happen to be AUX events (which is not the case the other
way around, because arch/s390), this changes the rules for stopping the
output: the AUX event may not be on its PMU's context any more, if it's
grouped with a HW event, in which case it will be on that HW event's
context instead. If that's the case, munmap() of the AUX buffer can't
find and stop the AUX event, potentially leaving the last reference with
the atomic context, which will then end up freeing the AUX buffer. This
will then trip warnings:

Fix this by using the context's PMU context when looking for events
to stop, instead of the event's PMU context.

Signed-off-by: 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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20191022073940.61814-1-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c651476b0e6a44448fcde9b94a99b50035d074f3..a4133d289e0184b0619b27d419cff7441e5d714f 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6470,7 +6470,7 @@ static void __perf_event_output_stop(struct perf_event *event, void *data)
 static int __perf_pmu_output_stop(void *info)
 {
        struct perf_event *event = info;
-       struct pmu *pmu = event->pmu;
+       struct pmu *pmu = event->ctx->pmu;
        struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
        struct remote_output ro = {
                .rb     = event->rb,