From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: iommu@lists.linux-foundation.org, Joerg Roedel <joro@8bytes.org>,
David Woodhouse <dwmw2@infradead.org>,
Lu Baolu <baolu.lu@linux.intel.com>,
Ashok Raj <ashok.raj@intel.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Jacob jun Pan <jacob.jun.pan@intel.com>,
Andreas Noever <andreas.noever@gmail.com>,
Michael Jamet <michael.jamet@intel.com>,
Yehezkel Bernat <YehezkelShB@gmail.com>,
Lukas Wunner <lukas@wunner.de>,
Christian Kellner <ckellner@redhat.com>,
Mario.Limonciello@dell.com,
Anthony Wong <anthony.wong@canonical.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Christoph Hellwig <hch@infradead.org>,
Alex Williamson <alex.williamson@redhat.com>,
linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/4] PCI / ACPI: Identify untrusted PCI devices
Date: Tue, 4 Dec 2018 10:57:35 +0200 [thread overview]
Message-ID: <20181204085735.GR3078@lahna.fi.intel.com> (raw)
In-Reply-To: <20181204002800.GB85090@google.com>
On Mon, Dec 03, 2018 at 06:28:00PM -0600, Bjorn Helgaas wrote:
> On Thu, Nov 29, 2018 at 06:51:50PM +0300, Mika Westerberg wrote:
> > 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.
> >
> > Recent BIOSes with Thunderbolt ports mark these externally facing root
> > ports with this ACPI _DSD [1]:
>
> I'm not 100% comfortable with the "Recent BIOSes" wording because that
> suggests that we can rely on the fact that *all* BIOSes newer than
> some date X mark these ports.
>
> Since this _DSD usage is Microsoft-specific and not required by either
> PCIe or ACPI specs, we can't rely on it. A BIOS that doesn't
> implement it may not be Windows-certified, but it's perfectly
> spec-compliant otherwise and we have to keep in mind the possibility
> that ports without this _DSD may still be externally visible and may
> still be attack vectors.
OK.
I will change it to "Some BIOSes .." following what you suggested
earlier. That should make it clear not all BIOSes are required to
implement this.
> > 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: Bjorn Helgaas <bhelgaas@google.com>
Thanks!
next prev parent reply other threads:[~2018-12-04 8:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-29 15:51 [PATCH v3 0/4] PCI / iommu / thunderbolt: IOMMU based DMA protection Mika Westerberg
2018-11-29 15:51 ` [PATCH v3 1/4] PCI / ACPI: Identify untrusted PCI devices Mika Westerberg
2018-11-29 20:59 ` Rafael J. Wysocki
2018-12-04 0:28 ` Bjorn Helgaas
2018-12-04 8:57 ` Mika Westerberg [this message]
2018-11-29 15:51 ` [PATCH v3 2/4] iommu/vt-d: Force IOMMU on for platform opt in hint Mika Westerberg
2018-11-29 15:51 ` [PATCH v3 3/4] iommu/vt-d: Do not enable ATS for untrusted devices Mika Westerberg
2018-11-29 15:51 ` [PATCH v3 4/4] thunderbolt: Export IOMMU based DMA protection support to userspace Mika Westerberg
2018-12-05 9:11 ` [PATCH v3 0/4] PCI / iommu / thunderbolt: IOMMU based DMA protection Mika Westerberg
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