On Tue, Feb 08, 2022 at 04:23:27PM -0800, Rajat Jain wrote:

Hello Folks,


On Tue, Feb 1, 2022 at 6:01 PM Rajat Jain [off-list ref] wrote:

quoted

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

quoted

Signed-off-by: Rajat Jain <redacted>
---
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)

Please no, "Untrusted" does not really convey much, if anything here.
You are taking an odd in-kernel-value and making it a user api.

Where is this "trust" defined?  Who defines it?  What policy does the
kernel impose on it?

By putting this value in a firmware requirement like this, it better be
documented VERY VERY well.

thanks,

greg k-h