Re: [PATCH] iommu/vt-d: Don't apply gfx quirks to untrusted devices

[Lu Baolu]

On 2020/6/2 13:45, 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.

Acked-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Best regards,
baolu

> Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx>
> ---
>   drivers/iommu/intel-iommu.c | 28 ++++++++++++++++++++++++++++
>   1 file changed, 28 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index ef0a5246700e5..f2a480168a02f 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -6214,6 +6214,11 @@ const struct iommu_ops intel_iommu_ops = {
>   
>   static void quirk_iommu_igfx(struct pci_dev *dev)
>   {
> +	if (dev->untrusted) {
> +		pci_warn(dev, "skipping iommu quirk for untrusted gfx dev\n");
> +		return;
> +	}
> +
>   	pci_info(dev, "Disabling IOMMU for graphics on this chipset\n");
>   	dmar_map_gfx = 0;
>   }
> @@ -6255,6 +6260,11 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x163D, quirk_iommu_igfx);
>   
>   static void quirk_iommu_rwbf(struct pci_dev *dev)
>   {
> +	if (dev->untrusted) {
> +		pci_warn(dev, "skipping iommu quirk for untrusted dev\n");
> +		return;
> +	}
> +
>   	/*
>   	 * Mobile 4 Series Chipset neglects to set RWBF capability,
>   	 * but needs it. Same seems to hold for the desktop versions.
> @@ -6285,6 +6295,11 @@ static void quirk_calpella_no_shadow_gtt(struct pci_dev *dev)
>   {
>   	unsigned short ggc;
>   
> +	if (dev->untrusted) {
> +		pci_warn(dev, "skipping iommu quirk for untrusted gfx dev\n");
> +		return;
> +	}
> +
>   	if (pci_read_config_word(dev, GGC, &ggc))
>   		return;
>   
> @@ -6318,6 +6333,13 @@ static void __init check_tylersburg_isoch(void)
>   	pdev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x3a3e, NULL);
>   	if (!pdev)
>   		return;
> +
> +	if (pdev->untrusted) {
> +		pci_warn(pdev, "skipping iommu quirk due to untrusted dev\n");
> +		pci_dev_put(pdev);
> +		return;
> +	}
> +
>   	pci_dev_put(pdev);
>   
>   	/* System Management Registers. Might be hidden, in which case
> @@ -6327,6 +6349,12 @@ static void __init check_tylersburg_isoch(void)
>   	if (!pdev)
>   		return;
>   
> +	if (pdev->untrusted) {
> +		pci_warn(pdev, "skipping iommu quirk due to untrusted dev\n");
> +		pci_dev_put(pdev);
> +		return;
> +	}
> +
>   	if (pci_read_config_dword(pdev, 0x188, &vtisochctrl)) {
>   		pci_dev_put(pdev);
>   		return;