Re: [PATCH -mm 4/7][AIO] - Make good_sigevent() non-static

Sébastien Dugué
2007-02-05T11:10:45Z

Hi Oleg,

thanks for your comments.

On Fri, 2 Feb 2007 21:00:39 +0300 Oleg Nesterov <oleg@tv-sign.ru> wrote:

> On 02/01, S?bastien Dugu? wrote:
> >
> > +struct task_struct * sigevent_find_task(sigevent_t * event)
> > +{
> > + struct task_struct *task = NULL;
> > +
> > + if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
> > + return NULL;
> > +
> > + if ((event->sigev_notify & SIGEV_THREAD_ID ) == SIGEV_THREAD_ID) {
> > + task = find_task_by_pid(event->sigev_notify_thread_id);
> > +
> > + if (!task || task->tgid != current->tgid)
> > + task = NULL;
> > + } else if (event->sigev_notify == SIGEV_SIGNAL)
> > + task = current->group_leader;
> > +
> > + return task;
> > +}
>
> I am afraid this is still not right. Consider
>
> ->sigev_notify == SIGEV_THREAD_ID | RANDOM_BIT
>
> Now, the second "if (SIGEV_THREAD_ID)" returns a valid task. However,
>
> really_put_req:
>
> if (notify == SIGEV_THREAD_ID || notify == SIGEV_SIGNAL)
> put_task_struct();
>
> doesn't work, so we have task_struct leak.

Right, I'll revert back to the old code with cleanups.

>
> Worse, this breaks posix-timers. Note that posix-timers allow SIGEV_NONE,
> the timer is not queued in that case, we shouldn't do ->sigev_signo check.
> This means that aio should check SIGEV_NONE itself.
>
> Also, it is critical for posix-timers that SIGEV_THREAD_ID doesn't come
> with another bit (like in the example below), note the code like
>
> if (sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
> ...
>
> IOW: good_sigevent() in its current form is very cryptic, and it _really_
> needs a cleanup, but we should not change its behaviour.

Yep. I must admit that I didn't pay enough attention to this 10-liner,
but in the end it rightfully backfired on me.

>
> Apart from this, I don't see other problems in the signal related code in
> this series.
>
> Oleg.
>

Thanks again for your review.

Sébastien.