From 971c90bfa2f0b4fe52d6d9002178d547706f1343 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Thu, 4 Aug 2011 07:25:35 -0700 Subject: alarmtimers: Avoid possible null pointer traversal We don't check if old_setting is non null before assigning it, so correct this. CC: Thomas Gleixner CC: stable@kernel.org Signed-off-by: John Stultz --- kernel/time/alarmtimer.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index 59f369f98a0..1dee3f62a6a 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -479,11 +479,8 @@ 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); + if (old_setting) + alarm_timer_get(timr, old_setting); /* If the timer was already set, cancel it */ alarm_cancel(&timr->it.alarmtimer); -- cgit v1.2.3-18-g5258 From ea7802f630d356acaf66b3c0b28c00a945fc35dc Mon Sep 17 00:00:00 2001 From: John Stultz Date: Thu, 4 Aug 2011 07:51:56 -0700 Subject: alarmtimers: Memset itimerspec passed into alarm_timer_get Following common_timer_get, zero out the itimerspec passed in. CC: Thomas Gleixner CC: stable@kernel.org Signed-off-by: John Stultz --- kernel/time/alarmtimer.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel') diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index 1dee3f62a6a..0e9263f6fd0 100644 --- 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 = -- cgit v1.2.3-18-g5258 From 6af7e471e5a7746b8024d70b4363d3dfe41d36b8 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Wed, 10 Aug 2011 10:26:09 -0700 Subject: alarmtimers: Avoid possible denial of service with high freq periodic timers Its possible to jam up the alarm timers by setting very small interval timers, which will cause the alarmtimer subsystem to spend all of its time firing and restarting timers. This can effectivly lock up a box. A deeper fix is needed, closely mimicking the hrtimer code, but for now just cap the interval to 100us to avoid userland hanging the system. CC: Thomas Gleixner CC: stable@kernel.org Signed-off-by: John Stultz --- kernel/time/alarmtimer.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'kernel') diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index 0e9263f6fd0..ea5e1a928d5 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -481,6 +481,15 @@ static int alarm_timer_set(struct k_itimer *timr, int flags, if (!rtcdev) return -ENOTSUPP; + /* + * 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); -- cgit v1.2.3-18-g5258