On 07/31, Christian Brauner wrote:
>
> It's currently possible to create pidfds for kthreads but it is unclear
> what that is supposed to mean. Until we have use-cases for it and we
> figured out what behavior we want block the creation of pidfds for
> kthreads.
Hmm... could you explain your concerns? Why do you think we should disallow
pidfd_open(pid-of-kthread) ?
> @@ -2403,6 +2416,12 @@ __latent_entropy struct task_struct *copy_process(
> if (clone_flags & CLONE_PIDFD) {
> int flags = (clone_flags & CLONE_THREAD) ? PIDFD_THREAD : 0;
>
> + /* Don't create pidfds for kernel threads for now. */
> + if (args->kthread) {
> + retval = -EINVAL;
> + goto bad_fork_free_pid;
Do we really need this check? Userspace can't use args->kthread != NULL,
the kernel users should not use CLONE_PIDFD.
Oleg.
