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posix-timers: Fix division by zero bug

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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 <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
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 <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Gleixner 2018-12-17 13:31:05 +01:00 committed by Greg Kroah-Hartman
parent 1f51527d02
commit 82c8dbb376
1 changed files with 1 additions and 4 deletions
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5
kernel/time/posix-timers.c
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@ -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;