lkml.org 
[lkml]   [2018]   [Dec]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] posix-timers: Prevent division by zero
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: stable@vger.kernel.org
---
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 kernel_sigi
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;
\
 
 \ /
  Last update: 2018-12-17 13:32    [W:0.048 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site