We expect to receive PFs with SR-IOV disabled, however some host
drivers leave SR-IOV enabled at unbind. This puts us in a state where
we can potentially assign both the PF and the VF, leading to both
functionality as well as security concerns due to lack of managing the
SR-IOV state as well as vendor dependent isolation from the PF to VF.
If we were to attempt to actively disable SR-IOV on driver probe, we
risk VF bound drivers blocking, potentially risking live lock
scenarios. Therefore simply refuse to bind to PFs with SR-IOV enabled
with a warning message indicating the issue. Users can resolve this
by re-binding to the host driver and disabling SR-IOV before
attempting to use the device with vfio-pci.
Signed-off-by: Alex Williamson <[email protected]>
---
drivers/vfio/pci/vfio_pci.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index b423a309a6e0..f372f209c5c2 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1189,6 +1189,19 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
return -EINVAL;
+ /*
+ * Prevent binding to PFs with VFs enabled, this too easily allows
+ * userspace instance with VFs and PFs from the same device, which
+ * cannot work. Disabling SR-IOV here would initiate removing the
+ * VFs, which would unbind the driver, which is prone to blocking
+ * if that VF is also in use by vfio-pci. Just reject these PFs
+ * and let the user sort it out.
+ */
+ if (pci_num_vf(pdev)) {
+ pci_warn(pdev, "Cannot bind to PF with SR-IOV enabled\n");
+ return -EBUSY;
+ }
+
group = vfio_iommu_group_get(&pdev->dev);
if (!group)
return -EINVAL;
On Thu, Jul 12, 2018 at 04:33:04PM -0600, Alex Williamson wrote:
> We expect to receive PFs with SR-IOV disabled, however some host
> drivers leave SR-IOV enabled at unbind. This puts us in a state where
> we can potentially assign both the PF and the VF, leading to both
> functionality as well as security concerns due to lack of managing the
> SR-IOV state as well as vendor dependent isolation from the PF to VF.
> If we were to attempt to actively disable SR-IOV on driver probe, we
> risk VF bound drivers blocking, potentially risking live lock
> scenarios. Therefore simply refuse to bind to PFs with SR-IOV enabled
> with a warning message indicating the issue. Users can resolve this
> by re-binding to the host driver and disabling SR-IOV before
> attempting to use the device with vfio-pci.
>
> Signed-off-by: Alex Williamson <[email protected]>
Reviewed-by: David Gibson <[email protected]>
> ---
> drivers/vfio/pci/vfio_pci.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index b423a309a6e0..f372f209c5c2 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -1189,6 +1189,19 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (pdev->hdr_type != PCI_HEADER_TYPE_NORMAL)
> return -EINVAL;
>
> + /*
> + * Prevent binding to PFs with VFs enabled, this too easily allows
> + * userspace instance with VFs and PFs from the same device, which
> + * cannot work. Disabling SR-IOV here would initiate removing the
> + * VFs, which would unbind the driver, which is prone to blocking
> + * if that VF is also in use by vfio-pci. Just reject these PFs
> + * and let the user sort it out.
> + */
> + if (pci_num_vf(pdev)) {
> + pci_warn(pdev, "Cannot bind to PF with SR-IOV enabled\n");
> + return -EBUSY;
> + }
> +
> group = vfio_iommu_group_get(&pdev->dev);
> if (!group)
> return -EINVAL;
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
On Thu, Jul 12, 2018 at 04:33:04PM -0600, Alex Williamson wrote:
> We expect to receive PFs with SR-IOV disabled, however some host
> drivers leave SR-IOV enabled at unbind. This puts us in a state where
> we can potentially assign both the PF and the VF, leading to both
> functionality as well as security concerns due to lack of managing the
> SR-IOV state as well as vendor dependent isolation from the PF to VF.
> If we were to attempt to actively disable SR-IOV on driver probe, we
> risk VF bound drivers blocking, potentially risking live lock
> scenarios. Therefore simply refuse to bind to PFs with SR-IOV enabled
> with a warning message indicating the issue. Users can resolve this
> by re-binding to the host driver and disabling SR-IOV before
> attempting to use the device with vfio-pci.
>
> Signed-off-by: Alex Williamson <[email protected]>
Reviewed-by: Peter Xu <[email protected]>
--
Peter Xu