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vfio/pci: Use pci_try_reset_function() on initial open

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Device lock bites again; if a device .remove() callback races a user
calling ioctl(VFIO_GROUP_GET_DEVICE_FD), the unbind request will hold
the device lock, but the user ioctl may have already taken a vfio_device
reference.  In the case of a PCI device, the initial open will attempt
to reset the device, which again attempts to get the device lock,
resulting in deadlock.  Use the trylock PCI reset interface and return
error on the open path if reset fails due to lock contention.

Link: https://lkml.org/lkml/2017/7/25/381
Reported-by: Wen Congyang <wencongyang2@huawei.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Alex Williamson 2017-07-26 14:33:15 -06:00
parent bb67b496c3
commit 9f47803503
1 changed files with 8 additions and 1 deletions
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9
drivers/vfio/pci/vfio_pci.c
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@ -226,7 +226,14 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
if (ret)
return ret;
vdev->reset_works = (pci_reset_function(pdev) == 0);
/* If reset fails because of the device lock, fail this path entirely */
ret = pci_try_reset_function(pdev);
if (ret == -EAGAIN) {
pci_disable_device(pdev);
return ret;
}
vdev->reset_works = !ret;
pci_save_state(pdev);
vdev->pci_saved_state = pci_store_saved_state(pdev);
if (!vdev->pci_saved_state)