[natty,natty/ti-omap4 CVE 1/1] perf: Fix software event overflow

[Andy Whitcroft]

From: Peter Zijlstra <a.p.zijlstra at chello.nl>

The below patch is for -stable only, upstream has a much larger patch
that contains the below hunk in commit a8b0ca17b80e92faab46ee7179ba9e99ccb61233

Vince found that under certain circumstances software event overflows
go wrong and deadlock. Avoid trying to delete a timer from the timer
callback.

Reported-by: Vince Weaver <vweaver1 at eecs.utk.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra at chello.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>

CVE-2011-2918
backported from commit 462fee3af72df0de7b60b96c525ffe8baf4db0f0 stable-3.0.y
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 kernel/perf_event.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index b2536bd..478ec5d 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4447,11 +4447,8 @@ static int __perf_event_overflow(struct perf_event *event, int nmi,
 	if (events && atomic_dec_and_test(&event->event_limit)) {
 		ret = 1;
 		event->pending_kill = POLL_HUP;
-		if (nmi) {
-			event->pending_disable = 1;
-			irq_work_queue(&event->pending);
-		} else
-			perf_event_disable(event);
+		event->pending_disable = 1;
+		irq_work_queue(&event->pending);
 	}
 
 	if (event->overflow_handler)
-- 
1.7.4.1