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authorMika Westerberg <mika.westerberg@linux.intel.com>2018-08-16 12:28:48 +0300
committerMika Westerberg <mika.westerberg@linux.intel.com>2018-12-05 12:01:55 +0300
commit617654aae50eb59dd98aa53fb562e850937f4cde (patch)
tree8daf2232117f9b2c759b6f9ae641eab55c0faacf /drivers/acpi/property.c
parent2595646791c319cadfdbf271563aac97d0843dc7 (diff)
downloadlinux-617654aae50eb59dd98aa53fb562e850937f4cde.tar.xz
PCI / ACPI: Identify untrusted PCI devices
A malicious PCI device may use DMA to attack the system. An external Thunderbolt port is a convenient point to attach such a device. The OS may use IOMMU to defend against DMA attacks. Some BIOSes mark these externally facing root ports with this ACPI _DSD [1]: Name (_DSD, Package () { ToUUID ("efcc06cc-73ac-4bc3-bff0-76143807c389"), Package () { Package () {"ExternalFacingPort", 1}, Package () {"UID", 0 } } }) If we find such a root port, mark it and all its children as untrusted. The rest of the OS may use this information to enable DMA protection against malicious devices. For instance the device may be put behind an IOMMU to keep it from accessing memory outside of what the driver has allocated for it. While at it, add a comment on top of prp_guids array explaining the possible caveat resulting when these GUIDs are treated equivalent. [1] https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-externally-exposed-pcie-root-ports Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'drivers/acpi/property.c')
-rw-r--r--drivers/acpi/property.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index 8c7c4583b52d..77abe0ec4043 100644
--- a/drivers/acpi/property.c
+++ b/drivers/acpi/property.c
@@ -24,6 +24,14 @@ static int acpi_data_get_property_array(const struct acpi_device_data *data,
acpi_object_type type,
const union acpi_object **obj);
+/*
+ * The GUIDs here are made equivalent to each other in order to avoid extra
+ * complexity in the properties handling code, with the caveat that the
+ * kernel will accept certain combinations of GUID and properties that are
+ * not defined without a warning. For instance if any of the properties
+ * from different GUID appear in a property list of another, it will be
+ * accepted by the kernel. Firmware validation tools should catch these.
+ */
static const guid_t prp_guids[] = {
/* ACPI _DSD device properties GUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
GUID_INIT(0xdaffd814, 0x6eba, 0x4d8c,
@@ -31,6 +39,9 @@ static const guid_t prp_guids[] = {
/* Hotplug in D3 GUID: 6211e2c0-58a3-4af3-90e1-927a4e0c55a4 */
GUID_INIT(0x6211e2c0, 0x58a3, 0x4af3,
0x90, 0xe1, 0x92, 0x7a, 0x4e, 0x0c, 0x55, 0xa4),
+ /* External facing port GUID: efcc06cc-73ac-4bc3-bff0-76143807c389 */
+ GUID_INIT(0xefcc06cc, 0x73ac, 0x4bc3,
+ 0xbf, 0xf0, 0x76, 0x14, 0x38, 0x07, 0xc3, 0x89),
};
static const guid_t ads_guid =