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mISDN: fix races between misdn_del_timer() and timer callback 

mark the victim with negative ->id if misdn_del_timer() finds it on
the list, have timer callback *not* move ones so marked to dev->expired

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2013-04-15 16:55:41 -04:00
parent c08c464d6f
commit 1b1089561c
1 changed files with 9 additions and 13 deletions
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22
drivers/isdn/mISDN/timerdev.c
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@ -163,7 +163,8 @@ dev_expire_timer(unsigned long data)
u_long flags;
spin_lock_irqsave(&timer->dev->lock, flags);
list_move_tail(&timer->list, &timer->dev->expired);
if (timer->id >= 0)
list_move_tail(&timer->list, &timer->dev->expired);
spin_unlock_irqrestore(&timer->dev->lock, flags);
wake_up_interruptible(&timer->dev->wait);
}
@ -203,26 +204,21 @@ misdn_add_timer(struct mISDNtimerdev *dev, int timeout)
static int
misdn_del_timer(struct mISDNtimerdev *dev, int id)
{
u_long flags;
struct mISDNtimer *timer;
int ret = 0;
spin_lock_irqsave(&dev->lock, flags);
spin_lock_irq(&dev->lock);
list_for_each_entry(timer, &dev->pending, list) {
if (timer->id == id) {
list_del_init(&timer->list);
/* RED-PEN AK: race -- timer can be still running on
* other CPU. Needs reference count I think
*/
del_timer(&timer->tl);
ret = timer->id;
timer->id = -1;
spin_unlock_irq(&dev->lock);
del_timer_sync(&timer->tl);
kfree(timer);
goto unlock;
return id;
}
}
unlock:
spin_unlock_irqrestore(&dev->lock, flags);
return ret;
spin_unlock_irq(&dev->lock);
return 0;
}
static long