Re: [PATCH v4 2/4] pidfd: add CLONE_PIDFD_AUTOKILL

[Oleg Nesterov]

On 02/23, Christian Brauner wrote:
>
> @@ -2259,13 +2268,20 @@ __latent_entropy struct task_struct *copy_process(
>  	 * if the fd table isn't shared).
>  	 */
>  	if (clone_flags & CLONE_PIDFD) {
> -		int flags = (clone_flags & CLONE_THREAD) ? PIDFD_THREAD : 0;
> +		unsigned flags = PIDFD_STALE;
> +
> +		if (clone_flags & CLONE_THREAD)
> +			flags |= PIDFD_THREAD;
> +		if (clone_flags & CLONE_PIDFD_AUTOKILL) {
> +			task_set_no_new_privs(p);
> +			flags |= PIDFD_AUTOKILL;
> +		}
>  
>  		/*
>  		 * Note that no task has been attached to @pid yet indicate
>  		 * that via CLONE_PIDFD.
>  		 */
> -		retval = pidfd_prepare(pid, flags | PIDFD_STALE, &pidfile);
> +		retval = pidfd_prepare(pid, flags, &pidfile);

Confused... I think you also need to change pidfs_alloc_file() to restore
O_TRUNC after do_dentry_open() clears this flag? Just like it curently does

	pidfd_file->f_flags |= (flags & PIDFD_THREAD);

?

Oleg.