rtc: verify a critical argument to rtc_update_irq() before using it

This small addition to the core simplifies code in the drivers and makes
them more robust when handling shared IRQs.

Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 544be722937c..c2eff6082363 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -584,6 +584,9 @@ enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer)
 void rtc_update_irq(struct rtc_device *rtc,
                 unsigned long num, unsigned long events)
 {
+        if (unlikely(IS_ERR_OR_NULL(rtc)))
+                return;
+
         pm_stay_awake(rtc->dev.parent);
         schedule_work(&rtc->irqwork);
 }