Re: [PATCH -v5 07/14] futex: Change locking rules

[Peter Zijlstra]

On Tue, Mar 07, 2017 at 05:47:44PM +0100, Sebastian Andrzej Siewior wrote:
> On 2017-03-07 14:22:14 [+0100], Thomas Gleixner wrote:
> > Both 'return' statements leak &pi_state->pi_mutex.wait_lock ....
> 
> this has unlock in both 'return's.

>  handle_fault:
> +     raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
>       spin_unlock(q->lock_ptr);
>  
>       ret = fault_in_user_writeable(uaddr);
>  
>       spin_lock(q->lock_ptr);
> +     raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
>  
>       /*
>        * Check if someone else fixed it for us:
>        */
> -     if (pi_state->owner != oldowner)
> +     if (pi_state->owner != oldowner) {
> +             raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
>               return 0;
> +     }
>  
> -     if (ret)
> +     if (ret) {
> +             raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
>               return ret;
> +     }
>  
>       goto retry;
>  }

I had locally already fixed it with a common:

out_unlock:
  raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
  return ret;