Re: [PATCH 2/2] posix_timer: clean up properly if anything failsafter *_timer_create

[Andrew Vagin]

On 05/14/2010 10:48 PM, Oleg Nesterov wrote:
> On 05/14, Stanislaw Gruszka wrote:
>    
> > On Fri, 14 May 2010 18:03:57 +0200
> > Oleg Nesterov<oleg@xxxxxxxxxx>  wrote:
> >
> >      
> > > On 05/14, Andrey Vagin wrote:
> > >        
> > > > @@ -613,6 +613,8 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
> > > >   	 * and may cease to exist at any time.  Don't use or modify
> > > >   	 * new_timer after the unlock call.
> > > >   	 */
> > > > +out_cleanup:
> > > > +	CLOCK_DISPATCH(new_timer->it_clock, timer_cleanup, (new_timer));
> > > >          
> > > But at first glance you are right, posix_cpu_timer_create() does
> > > get_task_struct(it.cpu.task).
> > >        
> > If I understand problem correctly, seems to be fine to move
> > CLOCK_DISPATCH(which_clock, timer_create, (new_timer));
> > after all possible EFAULT errors and solve leak without creating
> > new timer_cleanup() callback.
> >      
> I thought about this too, we are doing copy_to_user(created_timer_id)
> "in advance" anyway. Probably we can move all this code block
>
> 	new_timer->it_id = (timer_t) new_timer_id;
> 	new_timer->it_clock = which_clock;
> 	new_timer->it_overrun = -1;
> 	error = CLOCK_DISPATCH(which_clock, timer_create, (new_timer));
> 	if (error)
> 		goto out;
>
> down, right before we take ->siglock.
>    
You are right. I will send a new patch sooner. Thanks for your comments.
> But I don't understand the change in posix_cpu_timer_del() from 1/2.
>    
timer_cleanup doesn't do the disarm timer. In case fail in timer_create 
it's enough to call timer_cleanup. This changes are not necessary in new 
version.
> Otoh, currently "The next step is hard to back out if there is an error"
> comment is not right, release_posix_timer() does put_pid(). We can
> move copy_to_user(created_timer_id) down after "if (timer_event_spec)"
> block too. (but before CLOCK_DISPATCH(), of course).
>
> Andrey, what do you think?
>    
I've look at code again and think that you are right. At first I created 
patches for 2.6.18 kernel, more complex code in this place and the 
comment "the next step is ..." induced me to make callback timer_cleanup.
> Oleg.
>
>    

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