Re: [RFC PATCH] Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

----- Original Message -----
> From: "Steven Rostedt" <rostedt@goodmis.org>
> To: "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>
> Cc: "Ingo Molnar" <mingo@kernel.org>, linux-kernel@vger.kernel.org, "Ingo Molnar" <mingo@redhat.com>, "Thomas
> Gleixner" <tglx@linutronix.de>, "Rusty Russell" <rusty@rustcorp.com.au>, "David Howells" <dhowells@redhat.com>,
> "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
> Sent: Thursday, February 13, 2014 10:28:17 AM
> Subject: Re: [RFC PATCH] Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE
> 
> On Thu, 13 Feb 2014 15:10:14 +0000 (UTC)
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> 
> > ----- Original Message -----
> > > From: "Steven Rostedt" <rostedt@goodmis.org>
> > > To: "Ingo Molnar" <mingo@kernel.org>
> > > Cc: "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
> > > linux-kernel@vger.kernel.org, "Ingo Molnar"
> > > <mingo@redhat.com>, "Thomas Gleixner" <tglx@linutronix.de>, "Rusty
> > > Russell" <rusty@rustcorp.com.au>, "David Howells"
> > > <dhowells@redhat.com>, "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>
> > > Sent: Tuesday, February 11, 2014 11:45:34 PM
> > > Subject: Re: [RFC PATCH] Fix: module signature vs tracepoints: add new
> > > TAINT_UNSIGNED_MODULE
> > > 
> > > 
> > [...]
> > > But if the kernel expects to have signed modules, and you force a
> > > module to be loaded that is not signed, then you still get that
> > > "forced" module taint, which is the same one as loading a module from
> > > an older kernel into a newer kernel. It's a different problem, and I
> > > can see having a different taint flag be more informative to kernel
> > > developers in general. I would welcome that change with or without
> > > letting tracepoints be set for that module.
> > 
> > There is one important inaccuracy in your explanation above: a
> > kernel supporting signed modules, but not enforcing "sig_force",
> > can load unsigned modules with a simple modprobe or insmod, without
> > any "--force" argument. Therefore, tainting the module as
> > "TAINT_FORCED_MODULE" is misleading.
> > 
> 
> Oh! You are saying that if the kernel only *supports* signed modules,
> and you load a module that is not signed, it will taint the kernel?

Yes, exactly, presuming that by "supporting" you mean CONFIG_MODULE_SIG=y.
Loading an unsigned module then taints the kernel, and taints the module
with TAINT_FORCED_MODULE even though "modprobe --force" was never used.

Thanks,

Mathieu

> 
> 
> -- Steve
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com