1 files changed, 21 insertions, 17 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index ee8d0ac1ebd2..2ee0497b42e2 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -301,6 +301,24 @@ unsigned long ktime_divns(const ktime_t kt, s64 div)
 }
 #endif /* BITS_PER_LONG >= 64 */
 
+/*
+ * Add two ktime values and do a safety check for overflow:
+ */
+
+ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs)
+{
+	ktime_t res = ktime_add(lhs, rhs);
+
+	/*
+	 * We use KTIME_SEC_MAX here, the maximum timeout which we can
+	 * return to user space in a timespec:
+	 */
+	if (res.tv64 < 0 || res.tv64 < lhs.tv64 || res.tv64 < rhs.tv64)
+		res = ktime_set(KTIME_SEC_MAX, 0);
+
+	return res;
+}
+
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
@@ -658,13 +676,7 @@ hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
 		 */
 		orun++;
 	}
-	timer->expires = ktime_add(timer->expires, interval);
-	/*
-	 * Make sure, that the result did not wrap with a very large
-	 * interval.
-	 */
-	if (timer->expires.tv64 < 0)
-		timer->expires = ktime_set(KTIME_SEC_MAX, 0);
+	timer->expires = ktime_add_safe(timer->expires, interval);
 
 	return orun;
 }
@@ -815,7 +827,7 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
 	new_base = switch_hrtimer_base(timer, base);
 
 	if (mode == HRTIMER_MODE_REL) {
-		tim = ktime_add(tim, new_base->get_time());
+		tim = ktime_add_safe(tim, new_base->get_time());
 		/*
 		 * CONFIG_TIME_LOW_RES is a temporary way for architectures
 		 * to signal that they simply return xtime in
@@ -824,16 +836,8 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
 		 * timeouts. This will go away with the GTOD framework.
 		 */
 #ifdef CONFIG_TIME_LOW_RES
-		tim = ktime_add(tim, base->resolution);
+		tim = ktime_add_safe(tim, base->resolution);
 #endif
-		/*
-		 * Careful here: User space might have asked for a
-		 * very long sleep, so the add above might result in a
-		 * negative number, which enqueues the timer in front
-		 * of the queue.
-		 */
-		if (tim.tv64 < 0)
-			tim.tv64 = KTIME_MAX;
 	}
 	timer->expires = tim;