[tip:perf/urgent] perf/core: Add sanity check to deal with pinned event failure

[tip-bot for Reinette Chatre <tipbot@zytor.com>]

Commit-ID:  befb1b3c2703897c5b8ffb0044dc5d0e5f27c5d7
Gitweb:     https://git.kernel.org/tip/befb1b3c2703897c5b8ffb0044dc5d0e5f27c5d7
Author:     Reinette Chatre <reinette.chatre@intel.com>
AuthorDate: Wed, 19 Sep 2018 10:29:06 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 28 Sep 2018 22:44:53 +0200

perf/core: Add sanity check to deal with pinned event failure

It is possible that a failure can occur during the scheduling of a
pinned event. The initial portion of perf_event_read_local() contains
the various error checks an event should pass before it can be
considered valid. Ensure that the potential scheduling failure
of a pinned event is checked for and have a credible error.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: fenghua.yu@intel.com
Cc: tony.luck@intel.com
Cc: acme@kernel.org
Cc: gavin.hindman@intel.com
Cc: jithu.joseph@intel.com
Cc: dave.hansen@intel.com
Cc: hpa@zytor.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/6486385d1f30336e9973b24c8c65f5079543d3d3.1537377064.git.reinette.chatre@intel.com

---
 kernel/events/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c80549bf82c6..dcb093e7b377 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3935,6 +3935,12 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
 		goto out;
 	}
 
+	/* If this is a pinned event it must be running on this CPU */
+	if (event->attr.pinned && event->oncpu != smp_processor_id()) {
+		ret = -EBUSY;
+		goto out;
+	}
+
 	/*
 	 * If the event is currently on this CPU, its either a per-task event,
 	 * or local to this CPU. Furthermore it means its ACTIVE (otherwise