Re: [PATCH v1 2/4] clone: add CLONE_PIDFD

[Oleg Nesterov]

On 04/16, Christian Brauner wrote:
>
> +	if (clone_flags & CLONE_PIDFD) {
> +		retval = pidfd_create(pid, &pidfdf);
> +		if (retval < 0)
> +			goto bad_fork_free_pid;
> +		pidfd = retval;
> +	}

...

> +	if (clone_flags & CLONE_PIDFD) {
> +		fd_install(pidfd, pidfdf);
> +		put_user(pidfd, parent_tidptr);

put_user() can fail, I don't think this error should be silently ignored,
this can lead to the hard-to-trigger/debug problems.

Why can't we do put_user-with-check along with pidfd_create() above?

Oleg.