4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: John Stultz <john.stultz@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: sboyd@xxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Cc: syzkaller-bugs@xxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1812171328050.1880@xxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/time/posix-timers.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -289,9 +289,6 @@ static void common_hrtimer_rearm(struct { 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 *in 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;
