alarmtimer: ensure RTC module is not unloaded

When registering the rtc device to be used to handle alarm timers, get_device is used to ensure the device doesn't go away but the module can still be unloaded. Call try_module_get to ensure the rtc driver will not go away. Reported-by: Michal Simek <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]> Tested-by: Michal Simek <[email protected]> Signed-off-by: Michal Simek <[email protected]>
ahsanhussain · Aug 21, 2017 · 281097a · 281097a
1 parent 5e5e895
commit 281097a
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
@@ -25,6 +25,8 @@
 #include <linux/posix-timers.h>
 #include <linux/workqueue.h>
 #include <linux/freezer.h>
+#include <linux/module.h>
+
 
 /**
  * struct alarm_base - Alarm timer bases
@@ -88,6 +90,11 @@ static int alarmtimer_rtc_add_device(struct device *dev,
 
 	spin_lock_irqsave(&rtcdev_lock, flags);
 	if (!rtcdev) {
+		if (!try_module_get(rtc->owner)) {
+			spin_unlock_irqrestore(&rtcdev_lock, flags);
+			return -1;
+		}
+
 		rtcdev = rtc;
 		/* hold a reference so it doesn't go away */
 		get_device(dev);