From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Mon, 19 Jun 2017 14:17:21 +0000 (+0800)
Subject: 4.4-stable patches
X-Git-Tag: v4.11.7~14
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=56bf80e4839603b9d5bba00a1c8255c63977f5d1;p=thirdparty%2Fkernel%2Fstable-queue.git

4.4-stable patches

added patches:
	alarmtimer-rate-limit-periodic-intervals.patch
---

diff --git a/queue-4.4/alarmtimer-rate-limit-periodic-intervals.patch b/queue-4.4/alarmtimer-rate-limit-periodic-intervals.patch
new file mode 100644
index 00000000000..66bc91ddcb9
--- /dev/null
+++ b/queue-4.4/alarmtimer-rate-limit-periodic-intervals.patch
@@ -0,0 +1,61 @@
+From ff86bf0c65f14346bf2440534f9ba5ac232c39a0 Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Tue, 30 May 2017 23:15:35 +0200
+Subject: alarmtimer: Rate limit periodic intervals
+
+From: Thomas Gleixner <tglx@linutronix.de>
+
+commit ff86bf0c65f14346bf2440534f9ba5ac232c39a0 upstream.
+
+The alarmtimer code has another source of potentially rearming itself too
+fast. Interval timers with a very samll interval have a similar CPU hog
+effect as the previously fixed overflow issue.
+
+The reason is that alarmtimers do not implement the normal protection
+against this kind of problem which the other posix timer use:
+
+  timer expires -> queue signal -> deliver signal -> rearm timer
+
+This scheme brings the rearming under scheduler control and prevents
+permanently firing timers which hog the CPU.
+
+Bringing this scheme to the alarm timer code is a major overhaul because it
+lacks all the necessary mechanisms completely.
+
+So for a quick fix limit the interval to one jiffie. This is not
+problematic in practice as alarmtimers are usually backed by an RTC for
+suspend which have 1 second resolution. It could be therefor argued that
+the resolution of this clock should be set to 1 second in general, but
+that's outside the scope of this fix.
+
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Cc: Peter Zijlstra <peterz@infradead.org>
+Cc: Kostya Serebryany <kcc@google.com>
+Cc: syzkaller <syzkaller@googlegroups.com>
+Cc: John Stultz <john.stultz@linaro.org>
+Cc: Dmitry Vyukov <dvyukov@google.com>
+Link: http://lkml.kernel.org/r/20170530211655.896767100@linutronix.de
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+
+---
+ kernel/time/alarmtimer.c |    8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+--- a/kernel/time/alarmtimer.c
++++ b/kernel/time/alarmtimer.c
+@@ -611,6 +611,14 @@ static int alarm_timer_set(struct k_itim
+ 
+ 	/* start the timer */
+ 	timr->it.alarm.interval = timespec_to_ktime(new_setting->it_interval);
++
++	/*
++	 * 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)
++		timr->it.alarm.interval = ktime_set(0, TICK_NSEC);
++
+ 	exp = timespec_to_ktime(new_setting->it_value);
+ 	/* Convert (if necessary) to absolute time */
+ 	if (flags != TIMER_ABSTIME) {
diff --git a/queue-4.4/series b/queue-4.4/series
index 6f909803f27..b9bb1c9aecc 100644
--- a/queue-4.4/series
+++ b/queue-4.4/series
@@ -26,3 +26,4 @@ genirq-release-resources-in-__setup_irq-error-path.patch
 alarmtimer-prevent-overflow-of-relative-timers.patch
 usb-dwc3-exynos-fix-axius-clock-error-path-to-do-cleanup.patch
 mips-fix-bnezc-jialc-return-address-calculation.patch
+alarmtimer-rate-limit-periodic-intervals.patch