linux-kernel - [PATCH] vfio/pci: Allow VPD short read

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Message-ID: <20160601032829.31584.96315.stgit@gimli.home>
Date:	Tue, 31 May 2016 21:28:57 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	kvm@...r.kernel.org
Cc:	alex.williamson@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH] vfio/pci: Allow VPD short read

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

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 9360140..688691d 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -749,7 +749,8 @@ static int vfio_vpd_config_write(struct vfio_pci_device *vdev, int pos,
 		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);
 	}