[PATCH v4 2/5] pid: Add PIDFD_IOCTL_GETFD to fetch file descriptors from processes

[Andy Lutomirski]

On Wed, Dec 18, 2019 at 3:55 PM Sargun Dhillon <sargun at sargun.me> wrote:
>
> +
> +       if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
> +               file = ERR_PTR(-EPERM);
> +               goto out;
> +       }

I don't think this is MODE_READ.  By copying an fd from the task, you
can easily change its state.

IMO it would be really nice if pidfd could act more like a capability
here and carry a ptrace mode, for example.  But I guess it doesn't
right now.


--Andy