Re: [PATCH v2 0/5] pid: add pidfd_open()

[Christian Brauner]

On Sun, Mar 31, 2019 at 03:16:47PM -0700, Linus Torvalds wrote:
> On Sun, Mar 31, 2019 at 3:03 PM Christian Brauner <christian@xxxxxxxxxx> wrote:
> >
> > Thanks for the input. The problem Jann and I saw with this is that it
> > would be awkward to have the kernel open a file in some procfs instance,
> > since then userspace would have to specify which procfs instance the fd
> > should come from.
> 
> I would actually suggest we just make the rules be that the
> pidfd_open() always return the internal /proc entry regardless of any
> mount-point (or any "hidepid") but also suggest that exactly *because*
> it gives you visibility into the target pid, you'd basically require
> the strictest kind of control of the process you're trying to get the
> pidfd of.
> 
> Ie likely something along the lines of
> 
>         ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS)

I can live with that but I would like to hear what Jann thinks too if
that's ok.

Christian