On Tue, Jun 02, 2020 at 04:26:02PM -0700, Rajat Jain wrote:
> Currently, an external malicious PCI device can masquerade the VID:PID
> of faulty gfx devices, and thus apply iommu quirks to effectively
> disable the IOMMU restrictions for itself.
>
> Thus we need to ensure that the device we are applying quirks to, is
> indeed an internal trusted device.
>
> Signed-off-by: Rajat Jain <raja...@google.com>
> Acked-by: Lu Baolu <baolu...@linux.intel.com>
With these changes
Reviewed-by: Ashok Raj <ashok....@intel.com>
> ---
> v3: - Separate out the warning mesage in a function to be called from
> other places. Change the warning string as suggested.
> v2: - Change the warning print strings.
> - Add Lu Baolu's acknowledgement.
>
> drivers/iommu/intel-iommu.c | 37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index ef0a5246700e5..dc859f02985a0 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -6185,6 +6185,23 @@ intel_iommu_domain_set_attr(struct iommu_domain
> *domain,
> return ret;
> }
>
> +/*
> + * Check that the device does not live on an external facing PCI port that is
> + * marked as untrusted. Such devices should not be able to apply quirks and
> + * thus not be able to bypass the IOMMU restrictions.
> + */
> +static bool risky_device(struct pci_dev *pdev)
> +{
> + if (pdev->untrusted) {
> + pci_warn(pdev,
> + "Skipping IOMMU quirk for dev (%04X:%04X) on untrusted"
> + " PCI link. Please check with your BIOS/Platform"
> + " vendor about this\n", pdev->vendor, pdev->device);
> + return true;
> + }
> + return false;
> +}
> +
> const struct iommu_ops intel_iommu_ops = {
> .capable = intel_iommu_capable,
> .domain_alloc = intel_iommu_domain_alloc,
> @@ -6214,6 +6231,9 @@ const struct iommu_ops intel_iommu_ops = {
>
> static void quirk_iommu_igfx(struct pci_dev *dev)
> {
> + if (risky_device(dev))
> + return;
> +
> pci_info(dev, "Disabling IOMMU for graphics on this chipset\n");
> dmar_map_gfx = 0;
> }
> @@ -6255,6 +6275,9 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x163D,
> quirk_iommu_igfx);
>
> static void quirk_iommu_rwbf(struct pci_dev *dev)
> {
> + if (risky_device(dev))
> + return;
> +
> /*
> * Mobile 4 Series Chipset neglects to set RWBF capability,
> * but needs it. Same seems to hold for the desktop versions.
> @@ -6285,6 +6308,9 @@ static void quirk_calpella_no_shadow_gtt(struct pci_dev
> *dev)
> {
> unsigned short ggc;
>
> + if (risky_device(dev))
> + return;
> +
> if (pci_read_config_word(dev, GGC, &ggc))
> return;
>
> @@ -6318,6 +6344,12 @@ static void __init check_tylersburg_isoch(void)
> pdev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x3a3e, NULL);
> if (!pdev)
> return;
> +
> + if (risky_device(pdev)) {
> + pci_dev_put(pdev);
> + return;
> + }
> +
> pci_dev_put(pdev);
>
> /* System Management Registers. Might be hidden, in which case
> @@ -6327,6 +6359,11 @@ static void __init check_tylersburg_isoch(void)
> if (!pdev)
> return;
>
> + if (risky_device(pdev)) {
> + pci_dev_put(pdev);
> + return;
> + }
> +
> if (pci_read_config_dword(pdev, 0x188, &vtisochctrl)) {
> pci_dev_put(pdev);
> return;
> --
> 2.27.0.rc2.251.g90737beb825-goog
>
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