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

Oleg Nesterov
2024-05-23T09:35:09Z

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?

Oleg.