linux-kernel - Re: [RFC 1/5] user namespaces: Add a user_namespace as creator/owner of uts

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Date:	Fri, 17 Dec 2010 22:32:52 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Greg KH <greg@...ah.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <michael.kerrisk@...il.com>
Subject: Re: [RFC 1/5] user namespaces: Add a user_namespace as creator/owner of uts_namespace

Greg KH <greg@...ah.com> writes:

> On Fri, Dec 17, 2010 at 12:40:11PM -0800, Eric W. Biederman wrote:
>> Greg KH <greg@...ah.com> writes:
>> 
>> >> There are also major benefits to have the version of something that is
>> >> never freed never going away, because it means you can just reference it
>> >> in code.  So while I would be happy to say this is special don't use a
>> >> kref and roll the reference counting logic by hand, we aren't
>> >> dynamically allocating init_uts_ns any time soon.
>> >
>> > Why have a reference count at all if it's not needed or used here?
>> 
>> We have to reference count every other uts namespace.
>
> Ok, that makes sense, then also please dynamically create this one, do
> not create a static kref.

Nope.  It's a bad idea.  It messes up the kernel bootstrap if you do
that, and it makes this one structure different from every other
structure init_task uses.

Eric
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