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| author | Thomas Gleixner <tglx@linutronix.de> | 2017-05-30 23:15:34 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-06-26 07:13:10 +0200 |
| commit | aac7fa215e8fc795287328c2914aa123e7538690 (patch) | |
| tree | f2a14306bfa05385981973f723ab97cbaec6deb1 | |
| parent | 4d4d501cd7079d9052bb9ea6778f15491508f95e (diff) | |
| download | linux-stable-aac7fa215e8fc795287328c2914aa123e7538690.tar.gz linux-stable-aac7fa215e8fc795287328c2914aa123e7538690.tar.bz2 linux-stable-aac7fa215e8fc795287328c2914aa123e7538690.zip | |
alarmtimer: Prevent overflow of relative timers
commit f4781e76f90df7aec400635d73ea4c35ee1d4765 upstream.
Andrey reported a alartimer related RCU stall while fuzzing the kernel with
syzkaller.
The reason for this is an overflow in ktime_add() which brings the
resulting time into negative space and causes immediate expiry of the
timer. The following rearm with a small interval does not bring the timer
back into positive space due to the same issue.
This results in a permanent firing alarmtimer which hogs the CPU.
Use ktime_add_safe() instead which detects the overflow and clamps the
result to KTIME_SEC_MAX.
Reported-by: Andrey Konovalov <andreyknvl@google.com>
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/20170530211655.802921648@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/time/alarmtimer.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index 7fbba635a549..cfab9eb8bb1b 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -339,7 +339,7 @@ void alarm_start_relative(struct alarm *alarm, ktime_t start) { struct alarm_base *base = &alarm_bases[alarm->type]; - start = ktime_add(start, base->gettime()); + start = ktime_add_safe(start, base->gettime()); alarm_start(alarm, start); } EXPORT_SYMBOL_GPL(alarm_start_relative); @@ -425,7 +425,7 @@ u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval) overrun++; } - alarm->node.expires = ktime_add(alarm->node.expires, interval); + alarm->node.expires = ktime_add_safe(alarm->node.expires, interval); return overrun; } EXPORT_SYMBOL_GPL(alarm_forward); @@ -617,7 +617,7 @@ static int alarm_timer_set(struct k_itimer *timr, int flags, ktime_t now; now = alarm_bases[timr->it.alarm.alarmtimer.type].gettime(); - exp = ktime_add(now, exp); + exp = ktime_add_safe(now, exp); } alarm_start(&timr->it.alarm.alarmtimer, exp); |