Re: [PATCH v12 00/16] Introduce support for Dell SMBIOS over WMI

[Darren Hart <dvhart@infradead.org>]

On Fri, Nov 03, 2017 at 04:30:13PM +0000, Mario.Limonciello@dell.com wrote:
> > -----Original Message-----
> > From: Darren Hart [mailto:dvhart@infradead.org]
> > Sent: Thursday, November 2, 2017 7:50 PM
> > To: Limonciello, Mario <Mario_Limonciello@Dell.com>
> > Cc: Andy Shevchenko <andy.shevchenko@gmail.com>; LKML <linux-
> > kernel@vger.kernel.org>; platform-driver-x86@vger.kernel.org; Andy Lutomirski
> > <luto@kernel.org>; quasisec@google.com; pali.rohar@gmail.com;
> > rjw@rjwysocki.net; mjg59@google.com; hch@lst.de; Greg KH <greg@kroah.com>;
> > Alan Cox <gnomes@lxorguk.ukuu.org.uk>
> > Subject: Re: [PATCH v12 00/16] Introduce support for Dell SMBIOS over WMI
> > 
> > On Wed, Nov 01, 2017 at 02:25:21PM -0500, Mario Limonciello wrote:
> > > The existing way that the dell-smbios helper module and associated
> > > other drivers (dell-laptop, dell-wmi) communicate with the platform
> > > really isn't secure.  It requires creating a buffer in physical
> > > DMA32 memory space and passing that to the platform via SMM.
> > >
> > > Since the platform got a physical memory pointer, you've just got
> > > to trust that the platform has only modified (and accessed) memory
> > > within that buffer.
> > >
> > > Dell Platform designers recognize this security risk and offer a
> > > safer way to communicate with the platform over ACPI.  This is
> > > in turn exposed via a WMI interface to the OS.
> > >
> > > When communicating over WMI-ACPI the communication doesn't occur
> > > with physical memory pointers.  When the ASL is invoked, the fixed
> > > length ACPI buffer is copied to a small operating region.  The ASL
> > > will invoke the SMI, and SMM will only have access to this operating
> > > region.  When the ASL returns the buffer is copied back for the OS
> > > to process.
> > >
> > > This method of communication should also deprecate the usage of the
> > > dcdbas kernel module and software dependent upon it's interface.
> > > Instead offer a character device interface for communicating with this
> > > ASL method to allow userspace to use instead.
> > >
> > > To faciliate that this patch series introduces a generic way for WMI
> > > drivers to be able to create discoverable character devices with
> > > a predictable IOCTL interface through the WMI bus when desired.
> > > Requiring WMI drivers to explicitly ask for this functionality will
> > > act as an effective vendor whitelist to character device creation.
> > >
> > > Some of this work is the basis for what will be a proper interpreter
> > > of MOF in the kernel and controls for what drivers will be able to
> > > do with that MOF.
> > >
> > > NOTE: This patch series is intended to go on top of platform-drivers-x86
> > > linux-next.
> > >
> > > For convenience the entire series including those is also available here:
> > > https://github.com/dell/linux/tree/wmi-smbios
> > 
> > Queued for testing, thanks Mario.
> > 
> > --
> > Darren Hart
> > VMware Open Source Technology Center
> 
> Thanks Darren.  BTW Did you forget to push?  I didn't see it at the testing branch:
> http://git.infradead.org/users/dvhart/linux-platform-drivers-x86.git/shortlog/refs/heads/testing
> 
> Thanks,
> 

The workflow currently goes first to review-dvhart, which 0-day will pull from,
then to testing for integration, then to for-next. I plan to move it to testing
today.

-- 
Darren Hart
VMware Open Source Technology Center