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

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Date:   Tue,  1 Feb 2022 18:01:02 -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>
Cc:     Rajat Jain <rajatja@...gle.com>
Subject: [PATCH v2 1/2] PCI: Allow internal devices to be marked as untrusted

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.

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