linux-kernel - Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ do?

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Message-ID: <20090301222130.GA27198@us.ibm.com>
Date:	Sun, 1 Mar 2009 16:21:30 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-api@...r.kernel.org,
	containers@...ts.linux-foundation.org, hpa@...or.com,
	linux-kernel@...r.kernel.org,
	Dave Hansen <dave@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	viro@...iv.linux.org.uk, mpm@...enic.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, tglx@...utronix.de, xemul@...nvz.org
Subject: Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ
	do?

Quoting Alexey Dobriyan (adobriyan@...il.com):
> On Sun, Mar 01, 2009 at 02:02:31PM -0600, Serge E. Hallyn wrote:
> > Quoting Alexey Dobriyan (adobriyan@...il.com):
> > > On Fri, Feb 27, 2009 at 01:31:12AM +0300, Alexey Dobriyan wrote:
> > > > This is collecting and start of dumping part of cleaned up OpenVZ C/R
> > > > implementation, FYI.
> > > 
> > > OK, here is second version which shows what to do with shared objects
> > > (cr_dump_nsproxy(), cr_dump_task_struct()), introduced more checks
> > > (still no unlinked files) and dumps some more information including
> > > structures connections (cr_pos_*)
> > > 
> > > Dumping pids in under thinking because in OpenVZ pids are saved as
> > > numbers due to CLONE_NEWPID is not allowed in container. In presense
> > > of multiple CLONE_NEWPID levels this must present a big problem. Looks
> > > like there is now way to not dump pids as separate object.
> > > 
> > > As result, struct cr_image_pid is variable-sized, don't know how this will
> > > play later.
> > > 
> > > Also, pid refcount check for external pointers is busted right now,
> > > because /proc inode pins struct pid, so there is almost always refcount
> > > vs ->o_count mismatch.
> > > 
> > > No restore yet. ;-)
> > 
> > Hi Alexey,
> > 
> > thanks for posting this.  Of course there are some predictable responses
> > (I like the simplicity of pure in-kernel, Dave will not :) but this
> > needs to be posted to make us talk about it.
> > 
> > A few more comments that came to me while looking it over:
> > 
> > 1. cap_sys_admin check is unfortunate.  In discussions about Oren's
> > patchset we've agreed that not having that check from the outset forces
> > us to consider security with each new patch and feature, which is a good
> > thing.
> 
> Removing CAP_SYS_ADMIN on restore?

And checkpoint.

-serge
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