Re: [RFC][PATCH 01/20] pid: Intoduce the concept of a wid (wait id)

[ebiederm@xmission.com (Eric W. Biederman)]

Kirill Korotaev <dev@sw.ru> writes:

> Eric,
>
> 1. I would rename wid to wpid :)
:)

> 2. Maybe I'm missing something in the discussions, but why is it required? if
> you provide fully isolated pid spaces, why do you care for wid?
> And how ptrace can work at all if cldstop reports some pid, but child is not
> accessiable via ptrace()? and if it doesn't work, what are your changes for?

A good question.

My pid spaces while isolated from each other are connected together in
something that resembles the mount relationship when mounting a filesystem.

The init process of a child pspace is visible in the parent pspace,
by it's wid.  So you should be able to ptrace pid == 1.  The other
children remain inaccessible directly.

The idea was to do my very best to preserve the unix process tree when
constructing a separate pid space.

I have to admit I have not yet tested the ptrace corner case, or
digested all of it's ramifications.  Unless I have messed up somewhere
it should just work.

This visibility of the child tree by a single pid inside the parent
tree is why I think my approach doesn't suffer from most of the
problems a completely isolated pid space has.

In fact I would even be willing to look at it as a global but
hierarchical pid space if that proved an interesting case.
So you could have something like pkill(int sig, int which, char *pid_path).
Where pid_path is something like "1537/3/58", and which specified
what kind of pid you are talking about (thread, pid, process group...)

>From a security stand point I want the option of a fully isolated
group of processes, so there is a possibility of keeping secrets from
the system administrator, but there is no reason that needs to be tied
to a pid space.

Eric
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