Re: [PATCH 0/3 v2] seccomp: improve handling of SECCOMP_IOCTL_NOTIF_RECV

[Andrei Vagin]

On Thu, May 23, 2024 at 2:35 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> On 05/23, Andrei Vagin wrote:
> >
> > This patch set addresses two problems with the SECCOMP_IOCTL_NOTIF_RECV
> > ioctl:
> > * it doesn't return when the seccomp filter becomes unused (all tasks
> >   have exited).
> > * EPOLLHUP is triggered not when a task exits, but rather when its zombie
> >   is collected.
>
> It seems that 2/3 also fixes another minor problem.
>
> Suppose that a group leader installs the new filter without
> SECCOMP_FILTER_FLAG_TSYNC, exits, and becomes a zombie. It can't be
> released until all its sub-threads exit.
>
> After that, without 2/3, SECCOMP_FILTER_FLAG_TSYNC from any other thread
> can never succeed, seccomp_can_sync_threads() will check a zombie leader
> and is_ancestor() will fail.
>
> Right?

It is right. I can introduce a self test for this case too, but let's
do that in a separate patch set.

>
> Oleg.
>