On 23/05/2017 19:24, Bjorn Helgaas wrote:
> On Thu, Apr 20, 2017 at 04:31:25PM +0200, Marc Gonzalez wrote:
>> This driver is required to work around several hardware bugs in the
>> PCIe controller.
>>
>> NB: Revision 1 does not support legacy interrupts, or IO space.
>>
>> Signed-off-by: Marc Gonzalez <marc_gonza...@sigmadesigns.com>
>> ---
>> Documentation/devicetree/bindings/pci/tango-pcie.txt | 32 ++++++++
>> drivers/pci/host/Kconfig | 8 ++
>> drivers/pci/host/Makefile | 1 +
>> drivers/pci/host/pcie-tango.c | 161
>> +++++++++++++++++++++++++++++++++++++++
>> include/linux/pci_ids.h | 2 +
>> 5 files changed, 204 insertions(+)
>> ...
>
>> +static int smp8759_config_read(struct pci_bus *bus,
>> + unsigned int devfn, int where, int size, u32 *val)
>> +{
>> + int ret;
>> + struct pci_config_window *cfg = bus->sysdata;
>> + struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
>> +
>> + /*
>> + * QUIRK #1
>> + * Reads in configuration space outside devfn 0 return garbage.
>> + */
>> + if (devfn != 0)
>> + return PCIBIOS_FUNC_NOT_SUPPORTED;
>> +
>> + /*
>> + * QUIRK #2
>> + * Unfortunately, config and mem spaces are muxed.
>> + * Linux does not support such a setting, since drivers are free
>> + * to access mem space directly, at any time.
>> + * Therefore, we can only PRAY that config and mem space accesses
>> + * NEVER occur concurrently.
>> + */
>> + writel_relaxed(1, pcie->mux);
>> + ret = pci_generic_config_read(bus, devfn, where, size, val);
>> + writel_relaxed(0, pcie->mux);
>
> This is a major issue and possibly even a security problem.
> Unprivileged users can cause config accesses via lspci/setpci.
Since the host bridge doesn't support hotplug in any way,
how about setting a flag once enumeration is complete,
to prevent all future config accesses?
> I don't have a good suggestion for addressing it, but if you can't
> make this work reliably, you need at least a dev_err() in the probe
> function and probably a taint of the kernel (see add_taint()).
There is a chance that the issue will get fixed in rev2
of the bridge. But obviously, that won't help for rev1
already in the wild.
Regards.
