Re: [PATCH] exit: PR_SET_ANCHOR for marking processes as reapers for child processes

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

Lennart Poettering <mzxreary@0pointer.de> writes:

> On Thu, 04.03.10 15:08, Oleg Nesterov (oleg@redhat.com) wrote:
>
>> Should we clear ->child_anchor flags when the "sub-init" execs? Or,
>> at least, when the task changes its credentials? Probably not, but
>> dunno.
>
> Since this flag is only useful for a very well defined type of processes
> (i.e. session managers, supervising daemons, init systems) it might make
> sense to reset it automatically when privs are dropped or we exec
> something. After all, I don't see how we'd gain any useful functionality
> when we allow this flag to continue to be set. However we would
> certainly be on the safer side when we reset it, because that way it can
> never leak it to processes that are differently privileged or do not
> expect it.
>
> So, for the sake of being on the safe side, I think we should reset the
> flag on exec()/setuid().
>
>> It is a bit strange that PR_SET_ANCHOR acts per-thread, not per
>> process.
>
> Yes, I agree, this should be per-process indeed.

Have you take a look at the pid namespace?

Except for the fact it requires privilege to create it seems to do
what you want.  It is certainly what I have been using when I want
an inescapable environment.

If nothing else I get the feeling that what you are after is
a generalization of the child_reaper feature in the pid namespace
and yet you haven't touched any of that code.

Eric