linux-kernel - Re: [PATCH v7] PCI: imx6: limit DBI register length

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Date:   Tue, 26 Feb 2019 12:36:57 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     Trent Piepho <tpiepho@...inj.com>
Cc:     leonard.crestez@....com, hongxing.zhu@....com,
        linux-kernel@...r.kernel.org, jingoohan1@...il.com,
        lorenzo.pieralisi@....com, gustavo.pimentel@...opsys.com,
        linux-pci@...r.kernel.org, l.stach@...gutronix.de,
        bhelgaas@...gle.com
Subject: Re: [PATCH v7] PCI: imx6: limit DBI register length

On 25.02.2019 17:52, Trent Piepho wrote:
> On Mon, 2019-02-25 at 16:15 +0000, Leonard Crestez wrote:
>> On Mon, 2019-02-25 at 17:02 +0100, Stefan Agner wrote:
>> > Define the length of the DBI registers and limit config space to its
>> > length. This makes sure that the kernel does not access registers
>> > beyond that point, avoiding the following abort on a i.MX 6Quad:
>> >
>> > +static void imx6_pcie_quirk(struct pci_dev *dev)
>> > +{
>> > +	struct pci_bus *bus = dev->bus;
>> > +	struct pcie_port *pp = bus->sysdata;
>> > +
>> > +	if (bus->number == pp->root_bus_nr) {
>> > +		struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>> > +		struct imx6_pcie *imx6_pcie = to_imx6_pcie(pci);
>> > +
>> > +		/*
>> > +		 * Limit config length to avoid the kernel reading beyond
>> > +		 * the register set and causing an abort on i.MX 6Quad
>> > +		 */
>> > +		if (imx6_pcie->drvdata->dbi_length)
>> > +			dev->cfg_size = imx6_pcie->drvdata->dbi_length;
>> > +	}
>> > +}
>> > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_SYNOPSYS, 0xabcd, imx6_pcie_quirk);
>>
>> This looks like a default from SYNOPSYS so it likely run on other SOCs
>> using the DesignWare PCI IP and crash because of those unchecked casts.
> 
> Yes, it's used on IMX7d too.  But it's worse than that, there's a USB
> controller core that uses the same vendor and device id,
> PCI_DEVICE_ID_SYNOPSYS_HAPSUSB3.  The quirk for that one uses class ==
> PCI_CLASS_SERIAL_USB_DEVICE to avoid matching this PCI-e IP.  See
> thread "PCI: Check for USB xHCI class for HAPS platform"

Hm, I see, something like this should fix this:

DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_SYNOPSYS, 0xabcd,
			PCI_CLASS_BRIDGE_PCI, 8, imx6_pcie_quirk);


(this needs "PCI: Work around Synopsys duplicate Device ID (HAPS USB3,
NXP i.MX)" applied, which is in v5.0-rc8 already).

--
Stefan