linux-kernel - Re: [PATCH 4/7] firmware_class: perform new LSM checks

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Date:	Sat, 19 Jul 2014 17:22:15 +1000 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Kees Cook <keescook@...omium.org>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Ming Lei <ming.lei@...onical.com>,
	"Luis R. Rodriguez" <mcgrof@...e.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	James Morris <james.l.morris@...cle.com>,
	David Howells <dhowells@...hat.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	linux-firmware@...nel.org,
	linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: [PATCH 4/7] firmware_class: perform new LSM checks

On Fri, 18 Jul 2014, Kees Cook wrote:

> On Thu, Jul 17, 2014 at 8:41 PM, James Morris <jmorris@...ei.org> wrote:
> > On Mon, 14 Jul 2014, Kees Cook wrote:
> >
> >> This attaches LSM hooks to the existing firmware loading interfaces:
> >> filesystem-found firmware and demand-loaded blobs.
> >
> >>  static int fw_get_filesystem_firmware(struct device *device,
> >> @@ -640,6 +646,12 @@ static ssize_t firmware_loading_store(struct device *dev,
> >>               break;
> >>       case 0:
> >>               if (test_bit(FW_STATUS_LOADING, &fw_buf->status)) {
> >> +                     if (security_kernel_fw_from_file(NULL, fw_buf->data,
> >> +                                                      fw_buf->size)) {
> >> +                             fw_load_abort(fw_priv);
> >> +                             break;
> >> +                     }
> >> +
> >>                       set_bit(FW_STATUS_DONE, &fw_buf->status);
> >>                       clear_bit(FW_STATUS_LOADING, &fw_buf->status);
> >>
> >>
> >
> > Can you explain the loading store, and what the semantics are for an LSM
> > when a NULL is passed as the file?
> 
> I'm not sure what you mean by "loading store"?

The caller: firmware_loading_store()

> When NULL is passed as the file, it means that the firmware was passes
> a blob, and there is no file backing it:

Where does this blob come from, is cached, built into the kernel, or what?


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

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