[PATCH] hrtimer: check hrtimer with a NULL function

[Phil Chang]

simillar with timers, check for timer->function == NULL.
If the pointer is NULL, discard the request silently.

Signed-off-by: Phil Chang <phil.chang@xxxxxxxxxxxx>
---
 kernel/time/hrtimer.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 492c14aac642..72d6e7bc9cd9 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1297,9 +1297,13 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 
 	base = lock_hrtimer_base(timer, &flags);
 
+	if (!timer->function)
+		goto out;
+
 	if (__hrtimer_start_range_ns(timer, tim, delta_ns, mode, base))
 		hrtimer_reprogram(timer, true);
 
+out:
 	unlock_hrtimer_base(timer, &flags);
 }
 EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
@@ -1667,6 +1671,11 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
 	__remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
 	fn = timer->function;
 
+	if (WARN_ON_ONCE(!fn)) {
+		/* Should never happen. */
+		goto out;
+	}
+
 	/*
 	 * Clear the 'is relative' flag for the TIME_LOW_RES case. If the
 	 * timer is restarted with a period then it becomes an absolute
@@ -1710,6 +1719,7 @@ static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base,
 	 * hrtimer_active() cannot observe base->running.timer == NULL &&
 	 * timer->state == INACTIVE.
 	 */
+out:
 	raw_write_seqcount_barrier(&base->seq);
 
 	WARN_ON_ONCE(base->running != timer);
-- 
2.18.0