From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:49544 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752984AbdFRK7e (ORCPT ); Sun, 18 Jun 2017 06:59:34 -0400 Subject: Patch "alarmtimer: Prevent overflow of relative timers" has been added to the 4.9-stable tree To: tglx@linutronix.de, andreyknvl@google.com, dvyukov@google.com, gregkh@linuxfoundation.org, john.stultz@linaro.org, kcc@google.com, peterz@infradead.org, syzkaller@googlegroups.com Cc: , From: Date: Sun, 18 Jun 2017 18:59:22 +0800 Message-ID: <149778356254195@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled alarmtimer: Prevent overflow of relative timers to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alarmtimer-prevent-overflow-of-relative-timers.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From f4781e76f90df7aec400635d73ea4c35ee1d4765 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 30 May 2017 23:15:34 +0200 Subject: alarmtimer: Prevent overflow of relative timers From: Thomas Gleixner 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 Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Kostya Serebryany Cc: syzkaller Cc: John Stultz Cc: Dmitry Vyukov Link: http://lkml.kernel.org/r/20170530211655.802921648@linutronix.de Signed-off-by: Greg Kroah-Hartman --- kernel/time/alarmtimer.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -354,7 +354,7 @@ void alarm_start_relative(struct alarm * { 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); @@ -440,7 +440,7 @@ u64 alarm_forward(struct alarm *alarm, k 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); @@ -630,7 +630,7 @@ static int alarm_timer_set(struct k_itim 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); Patches currently in stable-queue which might be from tglx@linutronix.de are queue-4.9/genirq-release-resources-in-__setup_irq-error-path.patch queue-4.9/sched-core-idle_task_exit-shouldn-t-use-switch_mm_irqs_off.patch queue-4.9/x86-mm-32-set-the-__vmalloc_start_set-flag-in-initmem_init.patch queue-4.9/alarmtimer-prevent-overflow-of-relative-timers.patch