Re: [PATCH -mm 3/4][AIO] - AIO completion signal notification

[Sébastien Dugué]

On Thu, 23 Nov 2006 00:40:53 -0800
Andrew Morton <akpm@xxxxxxxx> wrote:

> On Thu, 23 Nov 2006 09:28:05 +0100
> Sébastien Dugué <sebastien.dugue@xxxxxxxx> wrote:
> 
> > > > +	target = good_sigevent(&event);
> > > > +
> > > > +	if (unlikely(!target || (target->flags & PF_EXITING)))
> > > > +		goto out_unlock;
> > > > +
> > > > +	
> > > > +
> > > > +	if (notify->notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID)) {
> > > > +		/*
> > > > +		 * This reference will be dropped in really_put_req() when
> > > > +		 * we're done with the request.
> > > > +		 */
> > > > +		get_task_struct(target);
> > > > +	}
> > > 
> > > It worries me that this function can save away a task_struct* without
> > > having taken a reference against it.
> > > 
> > 
> >   OK. Does moving 'notify->target = target;' after the get_task_struct() will
> > do, or am I missing something more subtle?
> 
> Well it's your code - you tell me ;)
> 
> It is unsafe (and rather pointless) to be saving the address of some structure
> which can be freed at any time.

  Sorry, I expressed myself quite badly. What I wanted to know is whether you
are worried with the task been freed between saving its pointer and getting a
ref on it (which is trivial to fix) or you are thinking of something deeper.

  Thanks,

  Sébastien.
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