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authorAlex Williamson <alex.williamson@redhat.com>2015-06-09 10:08:57 -0600
committerAlex Williamson <alex.williamson@redhat.com>2015-06-09 10:08:57 -0600
commit20f300175a1e150dae231e21dfa1fc4c6fcf4db6 (patch)
treee1ad32bedc25162d87b58fa61445b8000df6ce27 /drivers/vfio/pci
parentd4a4f75cd8f29cd9464a5a32e9224a91571d6649 (diff)
downloadblackbird-obmc-linux-20f300175a1e150dae231e21dfa1fc4c6fcf4db6.tar.gz
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vfio/pci: Fix racy vfio_device_get_from_dev() call
Testing the driver for a PCI device is racy, it can be all but complete in the release path and still report the driver as ours. Therefore we can't trust drvdata to be valid. This race can sometimes be seen when one port of a multifunction device is being unbound from the vfio-pci driver while another function is being released by the user and attempting a bus reset. The device in the remove path is found as a dependent device for the bus reset of the release path device, the driver is still set to vfio-pci, but the drvdata has already been cleared, resulting in a null pointer dereference. To resolve this, fix vfio_device_get_from_dev() to not take the dev_get_drvdata() shortcut and instead traverse through the iommu_group, vfio_group, vfio_device path to get a reference we can trust. Once we have that reference, we know the device isn't in transition and we can test to make sure the driver is still what we expect, so that we don't interfere with devices we don't own. Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Diffstat (limited to 'drivers/vfio/pci')
-rw-r--r--drivers/vfio/pci/vfio_pci.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index e9851add6f4e..964ad572aaee 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -1056,19 +1056,21 @@ struct vfio_devices {
static int vfio_pci_get_devs(struct pci_dev *pdev, void *data)
{
struct vfio_devices *devs = data;
- struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);
-
- if (pci_drv != &vfio_pci_driver)
- return -EBUSY;
+ struct vfio_device *device;
if (devs->cur_index == devs->max_index)
return -ENOSPC;
- devs->devices[devs->cur_index] = vfio_device_get_from_dev(&pdev->dev);
- if (!devs->devices[devs->cur_index])
+ device = vfio_device_get_from_dev(&pdev->dev);
+ if (!device)
return -EINVAL;
- devs->cur_index++;
+ if (pci_dev_driver(pdev) != &vfio_pci_driver) {
+ vfio_device_put(device);
+ return -EBUSY;
+ }
+
+ devs->devices[devs->cur_index++] = device;
return 0;
}
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