linux-kernel - Re: [PATCH v5 5/5] sidechannel: Linux Security Module for sidechannel

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Message-ID: <alpine.LRH.2.21.1809280744560.8410@namei.org>
Date:   Fri, 28 Sep 2018 07:45:00 +1000 (AEST)
From:   James Morris <jmorris@...ei.org>
To:     Casey Schaufler <casey.schaufler@...el.com>
cc:     kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
        dave.hansen@...el.com, deneen.t.dock@...el.com,
        kristen@...ux.intel.com, arjan@...ux.intel.com
Subject: Re: [PATCH v5 5/5] sidechannel: Linux Security Module for
 sidechannel

On Wed, 26 Sep 2018, Casey Schaufler wrote:

> +	/*
> +	 * Namespace checks. Considered safe if:
> +	 *	cgroup namespace is the same
> +	 *	User namespace is the same
> +	 *	PID namespace is the same
> +	 */
> +	if (current->nsproxy)
> +		ccgn = current->nsproxy->cgroup_ns;
> +	if (p->nsproxy)
> +		pcgn = p->nsproxy->cgroup_ns;
> +	if (ccgn != pcgn)
> +		return -EACCES;
> +	if (current->cred->user_ns != p->cred->user_ns)
> +		return -EACCES;
> +	if (task_active_pid_ns(current) != task_active_pid_ns(p))
> +		return -EACCES;
> +	return 0;

I really don't like the idea of hard-coding namespace security semantics 
in an LSM.  Also, I'm not sure if these semantics make any sense.

It least make it user configurable.


-- 
James Morris
<jmorris@...ei.org>