Re: [PATCH 2/2] exec: move core_pattern pipe helper into the crashing namespace

[Oleg Nesterov <oleg@redhat.com>]

On 09/17, Will Drewry wrote:
>
> On Fri, Sep 17, 2010 at 8:29 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > This looks overcomplicated to me, or I missed something.
> >
> > I do not understand why should we do this beforehand, and why we need
> > copy_namespaces_unattached().
> >
> > Can't you just pass current to umh_pipe_setup() (or another helper) as
> > the argument? Then this helper can copy ->fs and ->nsproxy itself.
>
> I wasn't sure if it was reasonable to pass the current task_struct
> over, but I certainly can.

Why not? current calls call_usermodehelper_exec(), it can't go away
until subprocess_info->init() returns, it sleeps on wait_for_completion().

> In practice, this seems to amount to just adding a refcount to all the
> namespaces and creating a new nsproxy which isn't really needed.  Most
> likely, doing what you've suggested above plus the copy_fs_struct and
> the swap out will do the trick.  I'll try it out and see.  That's make
> it much clearer I think.

Yes, just get_nsproxy() (like fork() does) should be fine in this case.

As for copying ->fs, I am not sure actually. core_pattern is global,
say it is "|/coredumper". If you change ->root, then exec can fail
because that binary is not visible to the coredumping process?

Probably we should move core_pattern into ->pid_ns, I dunno.

Oleg.