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

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Date:   Mon, 25 Feb 2019 16:15:57 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     "stefan@...er.ch" <stefan@...er.ch>
CC:     Richard Zhu <hongxing.zhu@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "gustavo.pimentel@...opsys.com" <gustavo.pimentel@...opsys.com>,
        "tpiepho@...inj.com" <tpiepho@...inj.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>
Subject: Re: [PATCH v7] PCI: imx6: limit DBI register length

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.

There might also be some way to configure pci ids before boot (not
sure, didn't check).

Maybe you should check the device driver name in the quirk function?

--
Regards,
Leonard