linux-kernel - Re: [PATCH 05/10] Containers(V10): Add container

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Message-ID: <20070531195631.GA16220@sergelap.austin.ibm.com>
Date:	Thu, 31 May 2007 14:56:31 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	menage@...gle.com, dev@...ru, xemul@...ru, serue@...ibm.com,
	vatsa@...ibm.com, ebiederm@...ssion.com, haveblue@...ibm.com,
	svaidy@...ux.vnet.ibm.com, balbir@...ibm.com, pj@....com,
	cpw@....com, ckrm-tech@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, containers@...ts.osdl.org,
	mbligh@...gle.com, rohitseth@...gle.com, devel@...nvz.org
Subject: Re: [PATCH 05/10] Containers(V10): Add container_clone() interface

Quoting Andrew Morton (akpm@...ux-foundation.org):
> On Tue, 29 May 2007 06:01:09 -0700 menage@...gle.com wrote:
> 
> > This patch adds support for container_clone(), a speculative interface
> > to creating new containers intended to be used for systems such as
> > namespace unsharing.
> > 
> > ...
> >
> > +
> > +static atomic_t namecnt;
> > +static void get_unused_name(char *buf)
> > +{
> > +	sprintf(buf, "node%d", atomic_inc_return(&namecnt));
> > +}
> 
> A stupid thing, but a sufficiently determined attacker could cause this to
> wrap.

Yeah, this was very consciously done as a "just make it work for now"
naming system.  If we want to stick with this naming, then I suppose we
could do a global bitmap.

But imo this naming is not very convenient - it would be nicer if we

	a) allowed users to specify a name (not sure how that would work
		logistically)
	b) made the namecnt variable for automatically named containers
		be per-directory.  I'd much rather see

		/containers/node1/node1
		/containers/node2
	than
		/containers/node1/node3
		/containers/node2

	(assuming /node2 was created between /node1 and /node1/node1 or
	/node1/node3)

thanks,
-serge
-
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