time: Catch invalid timespec sleep values in __timekeeping_inject_sleeptime

Arve suggested making sure we catch possible negative sleep time
intervals that could be passed into timekeeping_inject_sleeptime.

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

kernel/time/timekeeping.c

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 342408c..9d09777 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -604,6 +604,12 @@
  */
 static void __timekeeping_inject_sleeptime(struct timespec *delta)
 {
+	if (!timespec_valid(delta)) {
+		printk(KERN_WARN "__timekeeping_inject_sleeptime: Invalid "
+					"sleep delta value!\n");
+		return;
+	}
+
 	xtime = timespec_add(xtime, *delta);
 	wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
 	total_sleep_time = timespec_add(total_sleep_time, *delta);