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Date: Thu, 27 Sep 2018 23:19:28 +0000
From: "Schaufler, Casey" <casey.schaufler@...el.com>
To: James Morris <jmorris@...ei.org>, Casey Schaufler <casey@...aufler-ca.com>
CC: "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
"Dock, Deneen T" <deneen.t.dock@...el.com>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "Hansen, Dave" <dave.hansen@...el.com>,
"linux-security-module@...r.kernel.org"
<linux-security-module@...r.kernel.org>, "selinux@...ho.nsa.gov"
<selinux@...ho.nsa.gov>, "arjan@...ux.intel.com" <arjan@...ux.intel.com>
Subject: RE: [PATCH v5 5/5] sidechannel: Linux Security Module for
sidechannel
> -----Original Message-----
> From: James Morris [mailto:jmorris@...ei.org]
> Sent: Thursday, September 27, 2018 3:47 PM
> To: Casey Schaufler <casey@...aufler-ca.com>
> Cc: Schaufler, Casey <casey.schaufler@...el.com>; kristen@...ux.intel.com;
> kernel-hardening@...ts.openwall.com; Dock, Deneen T
> <deneen.t.dock@...el.com>; linux-kernel@...r.kernel.org; Hansen, Dave
> <dave.hansen@...el.com>; linux-security-module@...r.kernel.org;
> selinux@...ho.nsa.gov; arjan@...ux.intel.com
> Subject: Re: [PATCH v5 5/5] sidechannel: Linux Security Module for sidechannel
>
> On Thu, 27 Sep 2018, Casey Schaufler wrote:
>
> > On 9/27/2018 2:45 PM, James Morris wrote:
> > > 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.
> >
> > Checks on namespaces where explicitly requested.
>
> By whom and what is the rationale?
The rationale is to protect containers. Since those closest thing
there is to a definition of containers is "uses namespaces" that
becomes the focus. Separating them out does not make too much
sense as I would expect someone concerned with one to be concerned
with all.
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