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Date:   Fri, 28 Sep 2018 07:45:00 +1000 (AEST)
From:   James Morris <jmorris@namei.org>
To:     Casey Schaufler <casey.schaufler@intel.com>
cc:     kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov,
        dave.hansen@intel.com, deneen.t.dock@intel.com,
        kristen@linux.intel.com, arjan@linux.intel.com
Subject: Re: [PATCH v5 5/5] sidechannel: Linux Security Module for
 sidechannel
In-Reply-To: <20180926203446.2004-6-casey.schaufler@intel.com>
Message-ID: <alpine.LRH.2.21.1809280744560.8410@namei.org>
References: <20180926203446.2004-1-casey.schaufler@intel.com> <20180926203446.2004-6-casey.schaufler@intel.com>
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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@namei.org>