xen/time: Check that the per_cpu data structure has data before freeing.

We don't check whether the per_cpu data structure has actually
been freed in the past. This checks it and if it has been freed
in the past then just continues on without double-freeing.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 011f1bf85765..6a56ae092994 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -434,10 +434,13 @@ void xen_teardown_timer(int cpu)
         struct clock_event_device *evt;
         BUG_ON(cpu == 0);
         evt = &per_cpu(xen_clock_events, cpu).evt;
-        unbind_from_irqhandler(evt->irq, NULL);
-        evt->irq = -1;
-        kfree(per_cpu(xen_clock_events, cpu).name);
-        per_cpu(xen_clock_events, cpu).name = NULL;
+
+        if (evt->irq >= 0) {
+                unbind_from_irqhandler(evt->irq, NULL);
+                evt->irq = -1;
+                kfree(per_cpu(xen_clock_events, cpu).name);
+                per_cpu(xen_clock_events, cpu).name = NULL;
+        }
 }
 
 void xen_setup_cpu_clockevents(void)