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    SubjectRe: [PATCH 2/4] posix-timers: fix creation race
    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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