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authorJohn Stultz <john.stultz@linaro.org>2011-08-10 13:26:09 -0400
committerJohn Stultz <john.stultz@linaro.org>2011-08-10 13:26:09 -0400
commit6af7e471e5a7746b8024d70b4363d3dfe41d36b8 (patch)
tree33b1af81dfadefcc367307939acbb0d28c07c7c1 /kernel/time/alarmtimer.c
parentea7802f630d356acaf66b3c0b28c00a945fc35dc (diff)
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 <tglx@linutronix.de> CC: stable@kernel.org Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'kernel/time/alarmtimer.c')
-rw-r--r--kernel/time/alarmtimer.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 0e9263f6fd09..ea5e1a928d5b 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,
481 if (!rtcdev) 481 if (!rtcdev)
482 return -ENOTSUPP; 482 return -ENOTSUPP;
483 483
484 /*
485 * XXX HACK! Currently we can DOS a system if the interval
486 * period on alarmtimers is too small. Cap the interval here
487 * to 100us and solve this properly in a future patch! -jstultz
488 */
489 if ((new_setting->it_interval.tv_sec == 0) &&
490 (new_setting->it_interval.tv_nsec < 100000))
491 new_setting->it_interval.tv_nsec = 100000;
492
484 if (old_setting) 493 if (old_setting)
485 alarm_timer_get(timr, old_setting); 494 alarm_timer_get(timr, old_setting);
486 495