[PATCH 4.4 063/312] vfio/pci: Allow VPD short read

[Greg Kroah-Hartman]

From: Alex Williamson <alex.williamson@xxxxxxxxxx>

commit ce7585f3c4d76bca1dff4b66ae1ea32552954f9e upstream.

The size of the VPD area is not necessarily 4-byte aligned, so a
pci_vpd_read() might return less than 4 bytes.  Zero our buffer and
accept anything other than an error.  Intel X710 NICs exercise this.

Fixes: 4e1a635552d3 ("vfio/pci: Use kernel VPD access functions")
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/vfio/pci/vfio_pci_config.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -698,7 +698,8 @@ static int vfio_vpd_config_write(struct
 		if (pci_write_vpd(pdev, addr & ~PCI_VPD_ADDR_F, 4, &data) != 4)
 			return count;
 	} else {
-		if (pci_read_vpd(pdev, addr, 4, &data) != 4)
+		data = 0;
+		if (pci_read_vpd(pdev, addr, 4, &data) < 0)
 			return count;
 		*pdata = cpu_to_le32(data);
 	}