linux-kernel - [PATCH 4.9 125/125] alarmtimer: dont rate limit one-shot timers

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Message-Id: <20170725192021.231098927@linuxfoundation.org>
Date:   Tue, 25 Jul 2017 12:20:40 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ben Fennema <fennema@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 4.9 125/125] alarmtimer: dont rate limit one-shot timers

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Hackmann <ghackmann@...gle.com>

Commit ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals") sets a
minimum bound on the alarm timer interval.  This minimum bound shouldn't
be applied if the interval is 0.  Otherwise, one-shot timers will be
converted into periodic ones.

Fixes: ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals")
Reported-by: Ben Fennema <fennema@...gle.com>
Signed-off-by: Greg Hackmann <ghackmann@...gle.com>
Cc: stable@...r.kernel.org
Cc: John Stultz <john.stultz@...aro.org>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/time/alarmtimer.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -629,7 +629,8 @@ static int alarm_timer_set(struct k_itim
 	 * Rate limit to the tick as a hot fix to prevent DOS. Will be
 	 * mopped up later.
 	 */
-	if (ktime_to_ns(timr->it.alarm.interval) < TICK_NSEC)
+	if (timr->it.alarm.interval.tv64 &&
+			ktime_to_ns(timr->it.alarm.interval) < TICK_NSEC)
 		timr->it.alarm.interval = ktime_set(0, TICK_NSEC);
 
 	exp = timespec_to_ktime(new_setting->it_value);