Messages in this thread | | | Date | Sun, 12 Aug 2007 23:44:55 +0400 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/4] posix-timers: fix creation race |
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On 08/12, Thomas Gleixner wrote: > > On Sun, 2007-08-12 at 21:05 +0400, Oleg Nesterov wrote: > > sys_timer_create() sets ->it_process and unlocks ->siglock, then checks > > tmr->it_sigev_notify to define if get_task_struct() is needed. > > > > We already passed ->it_id to the caller, another thread can delete this > > timer and free its memory in between. > > > > As a minimal fix, move this code under ->siglock, sys_timer_delete() takes > > it too before calling release_posix_timer(). A proper serialization would > > be to take ->it_lock, we add a partly initialized timer on posix_timers_id, > > not good. > > > > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> > > Acked-by: Thomas Gleixner <tglx@linutronix.de>
Oooh, thanks, but...
> > --- t/kernel/posix-timers.c~2_CREATE 2007-08-12 17:59:17.000000000 +0400 > > +++ t/kernel/posix-timers.c 2007-08-12 18:11:33.000000000 +0400 > > @@ -547,13 +547,12 @@ sys_timer_create(const clockid_t which_c > > new_timer->it_process = process; > > list_add(&new_timer->list, > > &process->signal->posix_timers); > > - spin_unlock_irqrestore(&process->sighand->siglock, flags); > > if (new_timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID)) > > get_task_struct(process); > > } else { > > - spin_unlock_irqrestore(&process->sighand->siglock, flags); > > process = NULL; > > } > > + spin_unlock_irqrestore(&process->sighand->siglock, flags);
i'll resend this patch tomorrow. We can't do spin_unlock_irqrestore(&process->...) if we set process = NULL above.
This all needs a cleanup anyway. The PF_EXITING check and related comment are bogus.
Other patches do not depend on this one.
Oleg.
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