linux-kernel - Re: [PATCH v2 1/2] PCI: Allow internal devices to be marked as untrusted

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Message-ID: <CACK8Z6GmC7O3__RKwSEOQQ5Pde6h-LRz_5d+--V=CuB76cpe+w@mail.gmail.com>
Date:   Tue, 8 Feb 2022 16:23:27 -0800
From:   Rajat Jain <rajatja@...gle.com>
To:     Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rajat Jain <rajatxjain@...il.com>,
        Dmitry Torokhov <dtor@...gle.com>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Pavel Machek <pavel@...x.de>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v2 1/2] PCI: Allow internal devices to be marked as untrusted

Hello Folks,


On Tue, Feb 1, 2022 at 6:01 PM Rajat Jain <rajatja@...gle.com> wrote:
>
> Today the pci_dev->untrusted is set for any devices sitting downstream
> an external facing port (determined via "ExternalFacingPort" or the
> "external-facing" properties).
>
> However, currently there is no way for internal devices to be marked as
> untrusted.
>
> There are use-cases though, where a platform would like to treat an
> internal device as untrusted (perhaps because it runs untrusted firmware
> or offers an attack surface by handling untrusted network data etc).
>
> Introduce a new "UntrustedDevice" property that can be used by the
> firmware to mark any device as untrusted.

Just to unite the threads (from
https://www.spinics.net/lists/linux-pci/msg120221.html). I did reach
out to Microsoft but they haven't acknowledged my email. I also pinged
them again yesterday, but I suspect I may not be able to break the
ice. So this patch may be ready to go in my opinion.

I don't see any outstanding comments on this patch, but please let me
know if you have any comments.

Thanks & Best Regards,

Rajat


>
> Signed-off-by: Rajat Jain <rajatja@...gle.com>
> ---
> v2: * Also use the same property for device tree based systems.
>     * Add documentation (next patch)
>
>  drivers/pci/of.c       | 2 ++
>  drivers/pci/pci-acpi.c | 1 +
>  drivers/pci/pci.c      | 9 +++++++++
>  drivers/pci/pci.h      | 2 ++
>  4 files changed, 14 insertions(+)
>
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index cb2e8351c2cc..e8b804664b69 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -24,6 +24,8 @@ void pci_set_of_node(struct pci_dev *dev)
>                                                     dev->devfn);
>         if (dev->dev.of_node)
>                 dev->dev.fwnode = &dev->dev.of_node->fwnode;
> +
> +       pci_set_untrusted(dev);
>  }
>
>  void pci_release_of_node(struct pci_dev *dev)
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index a42dbf448860..2bffbd5c6114 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -1356,6 +1356,7 @@ void pci_acpi_setup(struct device *dev, struct acpi_device *adev)
>
>         pci_acpi_optimize_delay(pci_dev, adev->handle);
>         pci_acpi_set_external_facing(pci_dev);
> +       pci_set_untrusted(pci_dev);
>         pci_acpi_add_edr_notifier(pci_dev);
>
>         pci_acpi_add_pm_notifier(adev, pci_dev);
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 9ecce435fb3f..41e887c27004 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6869,3 +6869,12 @@ static int __init pci_realloc_setup_params(void)
>         return 0;
>  }
>  pure_initcall(pci_realloc_setup_params);
> +
> +void pci_set_untrusted(struct pci_dev *pdev)
> +{
> +       u8 val;
> +
> +       if (!device_property_read_u8(&pdev->dev, "UntrustedDevice", &val)
> +           && val)
> +               pdev->untrusted = 1;
> +}
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 3d60cabde1a1..6c273ce5e0ba 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -761,4 +761,6 @@ static inline pci_power_t mid_pci_get_power_state(struct pci_dev *pdev)
>  }
>  #endif
>
> +void pci_set_untrusted(struct pci_dev *pdev);
> +
>  #endif /* DRIVERS_PCI_H */
> --
> 2.35.0.rc2.247.g8bbb082509-goog
>