perf/core: Check return value of the perf_event_read() IPI

The call to smp_call_function_single in perf_event_read() may fail if
an invalid or not online CPU index is passed. Warn user if such bug is
present and return error.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.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: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1471467307-61171-2-git-send-email-davidcc@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index a5fc5c8cdfb0d4b8301d659d306219746ed00bc9..5650f5317e0c3bf48782349f1f3e64e2aa3d48a1 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3549,9 +3549,10 @@ static int perf_event_read(struct perf_event *event, bool group)
                        .group = group,
                        .ret = 0,
                };
-               smp_call_function_single(event->oncpu,
-                                        __perf_event_read, &data, 1);
-               ret = data.ret;
+               ret = smp_call_function_single(event->oncpu, __perf_event_read, &data, 1);
+               /* The event must have been read from an online CPU: */
+               WARN_ON_ONCE(ret);
+               ret = ret ? : data.ret;
        } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
                struct perf_event_context *ctx = event->ctx;
                unsigned long flags;