Re: [PATCH 2/2] Platform integrity information in sysfs (version 9)

[Daniel Gutson <daniel@eclypsium.com>]

On Wed, Oct 21, 2020 at 4:55 PM Daniel Gutson <daniel@eclypsium.com> wrote:
>
> On Fri, Oct 2, 2020 at 10:43 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Sep 30, 2020 at 01:37:14PM -0300, Daniel Gutson wrote:
> > > This patch exports the BIOS Write Enable (bioswe), BIOS
> > > Lock Enable (biosle), and the SMM BIOS Write Protect (SMM_BIOSWP) fields of
> > > the BIOS Control register using the platform-integrity misc kernel module.
> > > The idea is to keep adding more flags, not only from the BC but also from
> > > other registers in following versions.
> > >
> > > The goal is that the attributes are avilable to fwupd when SecureBoot
> > > is turned on.
> > >
> > > Signed-off-by: Daniel Gutson <daniel.gutson@eclypsium.com>
> >
> > The subject line doesn't match what this patch does, please fix that up.
> >
> > But there are more core issues in this patch:
> >
> > >
> > > ---
> > >  drivers/mtd/spi-nor/controllers/Kconfig       |  1 +
> > >  .../mtd/spi-nor/controllers/intel-spi-pci.c   | 75 ++++++++++++++-
> > >  .../spi-nor/controllers/intel-spi-platform.c  |  2 +-
> > >  drivers/mtd/spi-nor/controllers/intel-spi.c   | 91 ++++++++++++++++++-
> > >  drivers/mtd/spi-nor/controllers/intel-spi.h   |  9 +-
> > >  5 files changed, 171 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/mtd/spi-nor/controllers/Kconfig b/drivers/mtd/spi-nor/controllers/Kconfig
> > > index 5c0e0ec2e6d1..e7eaef506fc2 100644
> > > --- a/drivers/mtd/spi-nor/controllers/Kconfig
> > > +++ b/drivers/mtd/spi-nor/controllers/Kconfig
> > > @@ -29,6 +29,7 @@ config SPI_NXP_SPIFI
> > >
> > >  config SPI_INTEL_SPI
> > >       tristate
> > > +     depends on PLATFORM_INTEGRITY_DATA
> > >
> > >  config SPI_INTEL_SPI_PCI
> > >       tristate "Intel PCH/PCU SPI flash PCI driver (DANGEROUS)"
> > > diff --git a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > > index c72aa1ab71ad..644b1a6091dc 100644
> > > --- a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > > +++ b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> > > @@ -10,11 +10,19 @@
> > >  #include <linux/kernel.h>
> > >  #include <linux/module.h>
> > >  #include <linux/pci.h>
> > > +#include <linux/platform-integrity.h>
> > >
> > >  #include "intel-spi.h"
> > >
> > >  #define BCR          0xdc
> > >  #define BCR_WPD              BIT(0)
> > > +#define BCR_BLE              BIT(1)
> > > +#define BCR_SMM_BWP  BIT(5)
> > > +
> > > +struct cnl_spi_attr {
> > > +     struct device_attribute dev_attr;
> > > +     u32 mask;
> > > +};
> > >
> > >  static const struct intel_spi_boardinfo bxt_info = {
> > >       .type = INTEL_SPI_BXT,
> > > @@ -24,6 +32,70 @@ static const struct intel_spi_boardinfo cnl_info = {
> > >       .type = INTEL_SPI_CNL,
> > >  };
> > >
> > > +#ifdef CONFIG_PLATFORM_INTEGRITY_DATA
> > > +static ssize_t intel_spi_cnl_spi_attr_show(struct device *dev,
> > > +                                        struct device_attribute *attr,
> > > +                                        char *buf, u32 mask)
> > > +{
> > > +     u32 bcr;
> > > +
> > > +     if (dev->parent == NULL)
> > > +             return -EIO;
> > > +
> > > +     if (pci_read_config_dword(container_of(dev->parent, struct pci_dev, dev),
> > > +                               BCR, &bcr) != PCIBIOS_SUCCESSFUL)
> > > +             return -EIO;
> > > +
> > > +     return sprintf(buf, "%d\n", (int)!!(bcr & mask));
> > > +}
> > > +
> > > +static ssize_t bioswe_show(struct device *dev, struct device_attribute *attr,
> > > +                        char *buf)
> > > +{
> > > +     return intel_spi_cnl_spi_attr_show(dev, attr, buf, BCR_WPD);
> > > +}
> > > +static DEVICE_ATTR_RO(bioswe);
> > > +
> > > +static ssize_t biosle_show(struct device *dev, struct device_attribute *attr,
> > > +                        char *buf)
> > > +{
> > > +     return intel_spi_cnl_spi_attr_show(dev, attr, buf, BCR_BLE);
> > > +}
> > > +static DEVICE_ATTR_RO(biosle);
> > > +
> > > +static ssize_t smm_bioswp_show(struct device *dev, struct device_attribute *attr,
> > > +                            char *buf)
> > > +{
> > > +     return intel_spi_cnl_spi_attr_show(dev, attr, buf, BCR_SMM_BWP);
> > > +}
> > > +static DEVICE_ATTR_RO(smm_bioswp);
> > > +
> > > +static struct attribute *cnl_attrs[] = {
> > > +     &dev_attr_bioswe.attr,
> > > +     &dev_attr_biosle.attr,
> > > +     &dev_attr_smm_bioswp.attr,
> > > +     NULL
> > > +};
> > > +ATTRIBUTE_GROUPS(cnl);
> >
> > If you are forcing the driver to create the groups, then you are forcing
> > us to audit each driver and verify that the files are the same name and
> > such.  Put the files in the "common" code please, and if you really need
> > a way to get the data out, make that a callback or something.
>
> If I understand you correctly, you are asking the opposite that Arnd
> asked me in a
> previous patch version: he told me no new callbacks, just use the
> device attribute API.
> However I'm not sure I understand your proposal, do you mean to let
> the device attr
> stay in the driver file, and do the group inside the common part? Therefore,
> to pass a dev attributes array to the common part?
> If not, could you please explain your proposal again?


ping please.

>
> >
> > Also, this name "platform integrity" is really really generic, while in
> > reality you are describing something very specific.  Are you sure you
> > want that?
> >
> > thanks,
> >
> > greg k-h
>
>
>
> --
>
>
> Daniel Gutson
> Engineering Director
> Eclypsium, Inc.
>
>
> Below The Surface: Get the latest threat research and insights on
> firmware and supply chain threats from the research team at Eclypsium.
> https://eclypsium.com/research/#threatreport



-- 


Daniel Gutson
Engineering Director
Eclypsium, Inc.


Below The Surface: Get the latest threat research and insights on
firmware and supply chain threats from the research team at Eclypsium.
https://eclypsium.com/research/#threatreport