Re: [PATCH 3.14 186/228] PCI: Wrong register used to check pending traffic

Bjorn Helgaas
2014-06-11T21:16:05Z

On Sat, Jun 7, 2014 at 9:02 PM, Ben Hutchings <ben@decadent.org.uk> wrote:
> On Wed, 2014-06-04 at 16:23 -0700, Greg Kroah-Hartman wrote:
>> 3.14-stable review patch. If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: Gavin Shan <gwshan@linux.vnet.ibm.com>
>>
>> commit d0b4cc4e32705ff00d90d32da7783c266c702c04 upstream.
>>
>> The incorrect register offset is passed to pci_wait_for_pending(), which is
>> caused by commit 157e876ffe ("PCI: Add pci_wait_for_pending() (refactor
>> pci_wait_for_pending_transaction())").
>>
>> Fixes: 157e876ffe ("PCI: Add pci_wait_for_pending() (refactor pci_wait_for_pending_transaction())
>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>> Acked-by: Alex Williamson <alex.williamson@gmail.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>
>> ---
>> drivers/pci/pci.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -3043,7 +3043,8 @@ int pci_wait_for_pending_transaction(str
>> if (!pci_is_pcie(dev))
>> return 1;
>>
>> - return pci_wait_for_pending(dev, PCI_EXP_DEVSTA, PCI_EXP_DEVSTA_TRPND);
>> + return pci_wait_for_pending(dev, pci_pcie_cap(dev) + PCI_EXP_DEVSTA,
>> + PCI_EXP_DEVSTA_TRPND);
>> }
>> EXPORT_SYMBOL(pci_wait_for_pending_transaction);
>>
>> @@ -3085,7 +3086,7 @@ static int pci_af_flr(struct pci_dev *de
>> return 0;
>>
>> /* Wait for Transaction Pending bit clean */
>> - if (pci_wait_for_pending(dev, PCI_AF_STATUS, PCI_AF_STATUS_TP))
>> + if (pci_wait_for_pending(dev, pos + PCI_AF_STATUS, PCI_AF_STATUS_TP))
>> goto clear;
>>
>> dev_err(&dev->dev, "transaction is not cleared; "
>
> This still seems to be broken because pci_wait_for_pending() does
> pci_read_config_word() but PCI_AF_STATUS is not word-aligned.

I agree; this does seem broken. I think pci_read_config_word() will
return PCIBIOS_BAD_REGISTER_NUMBER without updating the value
returned, so I think we'll test garbage from the stack.

What do you think, Alex?

Bjorn