perf: Fix perf_init_event()

We ought to return -ENOENT when non of the registered PMUs
recognise the requested event.

This fixes a boot crash that occurs if no PMU is available
but the NMI watchdog tries to register an event.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index f395fb4d9b74..f29b52576ec1 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5236,12 +5236,15 @@ struct pmu *perf_init_event(struct perf_event *event)
         list_for_each_entry_rcu(pmu, &pmus, entry) {
                 int ret = pmu->event_init(event);
                 if (!ret)
-                        break;
+                        goto unlock;
+
                 if (ret != -ENOENT) {
                         pmu = ERR_PTR(ret);
-                        break;
+                        goto unlock;
                 }
         }
+        pmu = ERR_PTR(-ENOENT);
+unlock:
         srcu_read_unlock(&pmus_srcu, idx);
 
         return pmu;