linux-kernel - Re: [RFC PATCH 1/5] ima: extend clone() with IMA namespace support

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Date:   Tue, 25 Jul 2017 11:49:14 -0700
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     "Serge E. Hallyn" <serge@...lyn.com>,
        Mehmet Kayaalp <mkayaalp@...ux.vnet.ibm.com>
Cc:     Mehmet Kayaalp <mkayaalp@...binghamton.edu>,
        Yuqiong Sun <sunyuqiong1988@...il.com>,
        containers <containers@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        David Safford <david.safford@...com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        ima-devel <linux-ima-devel@...ts.sourceforge.net>,
        Yuqiong Sun <suny@...ibm.com>
Subject: Re: [RFC PATCH 1/5] ima: extend clone() with IMA namespace support

On Tue, 2017-07-25 at 12:53 -0500, Serge E. Hallyn wrote:
> On Thu, Jul 20, 2017 at 06:50:29PM -0400, Mehmet Kayaalp wrote:
> > 
> > From: Yuqiong Sun <suny@...ibm.com>
> > 
> > Add new CONFIG_IMA_NS config option.  Let clone() create a new IMA
> > namespace upon CLONE_NEWNS flag. Add ima_ns data structure in
> > nsproxy.
> > ima_ns is allocated and freed upon IMA namespace creation and exit.
> > Currently, the ima_ns contains no useful IMA data but only a dummy
> > interface. This patch creates the framework for namespacing the
> > different
> > aspects of IMA (eg. IMA-audit, IMA-measurement, IMA-appraisal).
> > 
> > Signed-off-by: Yuqiong Sun <suny@...ibm.com>
> > 
> > Changelog:
> > * Use CLONE_NEWNS instead of a new CLONE_NEWIMA flag
> 
> Hi,
> 
> So this means that every mount namespace clone will clone a new IMA
> namespace.  Is that really ok?

Based on what: space concerns (struct ima_ns is reasonably small)? or
whether tying it to the mount namespace is the correct thing to do.  On
the latter, it does seem that this should be a property of either the
mount or user ns rather than its own separate ns.  I could see a use
where even a container might want multiple ima keyrings within the
container (say containerised apache service with multiple tenants), so
instinct tells me that mount ns is the correct granularity for this.

James