Re: [PATCH v7 2/9] pidfd: Add missing sock updates for pidfd_getfd()

[Jann Horn]

On Thu, Jul 9, 2020 at 8:26 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> The sock counting (sock_update_netprioidx() and sock_update_classid())
> was missing from pidfd's implementation of received fd installation. Add
> a call to the new __receive_sock() helper.
[...]
> diff --git a/kernel/pid.c b/kernel/pid.c
[...]
> @@ -642,10 +643,12 @@ static int pidfd_getfd(struct pid *pid, int fd)
>         }
>
>         ret = get_unused_fd_flags(O_CLOEXEC);
> -       if (ret < 0)
> +       if (ret < 0) {
>                 fput(file);
> -       else
> +       } else {
>                 fd_install(ret, file);
> +               __receive_sock(file);
> +       }

__receive_sock() has to be before fd_install(), otherwise `file` can
be a dangling pointer.