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

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Date:   Tue, 26 Feb 2019 10:55:48 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Trent Piepho <tpiepho@...inj.com>, 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, Thinh Nguyen <thinh.nguyen@...opsys.com>
Subject: Re: [PATCH v7] PCI: imx6: limit DBI register length

On 25.02.2019 21:19, Bjorn Helgaas wrote:
> [+cc Thinh]
> 
> On Mon, Feb 25, 2019 at 10:52 AM Trent Piepho <tpiepho@...inj.com> 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"
> 
> If we could get these vendors to allocate their own Vendor/Device IDs,
> maybe we could consider a DECLARE_PCI_FIXUP_EARLY quirk that would fix
> up pdev->vendor and pdev->device?  That might be cleaner than
> cluttering all these quirks with details of this screwup.

According to www.pcilookup.com there is a vendor/product id allocated
for recovery mode (Freescale i.MX 6, 15a2:0054). Is this a real PCI id?
The same Vendor/Device ID is used for USB recovery...

--
Stefan