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SubjectRe: [PATCH -mm 3/4][AIO] - AIO completion signal notification
On Mon, 20 Nov 2006 15:22:52 +0100
S__bastien Dugu__ <sebastien.dugue@bull.net> wrote:

> +static long aio_setup_sigevent(struct aio_notify *notify,
> + struct sigevent __user *user_event)
> +{
> + sigevent_t event;
> + struct task_struct *target;
> +
> + if (copy_from_user(&event, user_event, sizeof (event)))
> + return -EFAULT;
> +
> + if (event.sigev_notify == SIGEV_NONE)
> + return 0;
> +
> + notify->notify = event.sigev_notify;
> + notify->signo = event.sigev_signo;
> + notify->value = event.sigev_value;
> +
> + read_lock(&tasklist_lock);
> + target = good_sigevent(&event);
> +
> + if (unlikely(!target || (target->flags & PF_EXITING)))
> + goto out_unlock;
> +
> + notify->target = target;
> +
> + 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.


> + read_unlock(&tasklist_lock);
> +
> + /*
> + * NOTE: we cannot free the sigqueue in the completion path as
> + * the signal may not have been delivered to the target task.
> + * Therefore it has to be freed in __sigqueue_free() when the
> + * signal is collected if si_code is SI_ASYNCIO.
> + */
> + notify->sigq = sigqueue_alloc();
> +
> + if (unlikely(!notify->sigq))
> + return -EAGAIN;
> +
> + return 0;
> +
> +out_unlock:
> + read_unlock(&tasklist_lock);
> + return -EINVAL;
> +}
-
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