Re: PATCH? fix unshare(NEWPID) && vfork()

[Oleg Nesterov <oleg@redhat.com>]

On 08/20, Andy Lutomirski wrote:
>
> On Mon, Aug 19, 2013 at 11:43 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> > On 08/19, Andy Lutomirski wrote:
> >>
> >> On Mon, Aug 19, 2013 at 11:33 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> >> >
> >> > So do you think this change is fine or not (ignoring the fact it needs
> >> > cleanups) ?
> >>
> >> I think that removing the CLONE_VM check is fine (although there are
> >> some other ones that should probably be removed as well), but I'm not
> >> sure if that check needs replacing with something else.
> >
> > OK, thanks... but I still can't understand.
> >
> > The patch I sent is equivalent to the new one below. I just tried to
> > unify it with another check in do_fork().
>
> I was confused.

Andy, I do not know how much you were confused, but I bet I am confused
much more ;)

> Currently (with or without your patch), vfork() followed by
> unshare(CLONE_NEWUSER) or unshare(CLONE_NEWPID) will unshare the VM.

Could you spell please?

We never unshare the VM. CLONE_VM in sys_unshare() paths just means
"fail unless ->mm is not shared".

Oleg.