x86: make clockevents more robust

detect zero event-device multiplicators - they then cause
division-by-zero crashes if a clockevent has been initialized
incorrectly.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 5fb139fef9fa..3e59fce6dd43 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -41,6 +41,11 @@ unsigned long clockevent_delta2ns(unsigned long latch,
 {
         u64 clc = ((u64) latch << evt->shift);
 
+        if (unlikely(!evt->mult)) {
+                evt->mult = 1;
+                WARN_ON(1);
+        }
+
         do_div(clc, evt->mult);
         if (clc < 1000)
                 clc = 1000;
@@ -151,6 +156,14 @@ static void clockevents_notify_released(void)
 void clockevents_register_device(struct clock_event_device *dev)
 {
         BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
+        /*
+         * A nsec2cyc multiplicator of 0 is invalid and we'd crash
+         * on it, so fix it up and emit a warning:
+         */
+        if (unlikely(!dev->mult)) {
+                dev->mult = 1;
+                WARN_ON(1);
+        }
 
         spin_lock(&clockevents_lock);