alarmtimers: Avoid possible denial of service with high freq periodic timers

[pandora-kernel.git] / kernel / time / alarmtimer.c

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 59f369f..ea5e1a9 100644 (file)
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -441,6 +441,8 @@ static int alarm_timer_create(struct k_itimer *new_timer)
 static void alarm_timer_get(struct k_itimer *timr,
                                struct itimerspec *cur_setting)
 {
+       memset(cur_setting, 0, sizeof(struct itimerspec));
+
        cur_setting->it_interval =
                        ktime_to_timespec(timr->it.alarmtimer.period);
        cur_setting->it_value =
@@ -479,11 +481,17 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
        if (!rtcdev)
                return -ENOTSUPP;
 
-       /* Save old values */
-       old_setting->it_interval =
-                       ktime_to_timespec(timr->it.alarmtimer.period);
-       old_setting->it_value =
-                       ktime_to_timespec(timr->it.alarmtimer.node.expires);
+       /*
+        * XXX HACK! Currently we can DOS a system if the interval
+        * period on alarmtimers is too small. Cap the interval here
+        * to 100us and solve this properly in a future patch! -jstultz
+        */
+       if ((new_setting->it_interval.tv_sec == 0) &&
+                       (new_setting->it_interval.tv_nsec < 100000))
+               new_setting->it_interval.tv_nsec = 100000;
+
+       if (old_setting)
+               alarm_timer_get(timr, old_setting);
 
        /* If the timer was already set, cancel it */
        alarm_cancel(&timr->it.alarmtimer);