linux-kernel - Re: [PATCH v2] iommu/vt-d: Don't apply gfx quirks to untrusted devices

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Date:   Tue, 2 Jun 2020 13:05:35 -0700
From:   "Raj, Ashok" <ashok.raj@...el.com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...el.com>,
        lalithambika.krishnakumar@...el.com, rajatxjain@...il.com,
        pmalani@...gle.com, bleung@...gle.com, levinale@...gle.com,
        zsm@...gle.com, mnissler@...gle.com, tbroch@...gle.com,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH v2] iommu/vt-d: Don't apply gfx quirks to untrusted
 devices

Hi Rajat

On Tue, Jun 02, 2020 at 11:41:33AM -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 <rajatja@...gle.com>
> Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
> V2: - Change the warning print strings.
>     - Add Lu Baolu's acknowledgement.
> 
>  drivers/iommu/intel-iommu.c | 38 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index ef0a5246700e5..fdfbea4ff8cb3 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -6214,6 +6214,13 @@ 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 %s() for potentially untrusted device\n",
> +			 __func__);
> +		return;
> +	}
> +

This check and code seems to be happening several times. Maybe add a simple
function to do the test and use in all places?

Cheers,
Ashok