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

Oleg Nesterov
2007-02-02T18:00:54Z

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.

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.

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

Oleg.