From 82c8dbb376b9fa9b831c157cbb15664cb4a343e3 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 17 Dec 2018 13:31:05 +0100 Subject: posix-timers: Fix division by zero bug commit 0e334db6bb4b1fd1e2d72c1f3d8f004313cd9f94 upstream. The signal delivery path of posix-timers can try to rearm the timer even if the interval is zero. That's handled for the common case (hrtimer) but not for alarm timers. In that case the forwarding function raises a division by zero exception. The handling for hrtimer based posix timers is wrong because it marks the timer as active despite the fact that it is stopped. Move the check from common_hrtimer_rearm() to posixtimer_rearm() to cure both issues. Reported-by: syzbot+9d38bedac9cc77b8ad5e@syzkaller.appspotmail.com Signed-off-by: Thomas Gleixner Cc: John Stultz Cc: Linus Torvalds Cc: Peter Zijlstra Cc: sboyd@kernel.org Cc: stable@vger.kernel.org Cc: syzkaller-bugs@googlegroups.com Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1812171328050.1880@nanos.tec.linutronix.de Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/time/posix-timers.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 4b9127e95430..5a01c4fdbfef 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -289,9 +289,6 @@ static void common_hrtimer_rearm(struct k_itimer *timr) { struct hrtimer *timer = &timr->it.real.timer; - if (!timr->it_interval) - return; - timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), timr->it_interval); hrtimer_restart(timer); @@ -317,7 +314,7 @@ void posixtimer_rearm(struct siginfo *info) if (!timr) return; - if (timr->it_requeue_pending == info->si_sys_private) { + if (timr->it_interval && timr->it_requeue_pending == info->si_sys_private) { timr->kclock->timer_rearm(timr); timr->it_active = 1; -- cgit v1.2.3