vfio/pci: Clear error and request eventfd ctx after releasing

[ Upstream commit 5c5866c593bbd444d0339ede6a8fb5f14ff66d72 ]

The next use of the device will generate an underflow from the
stale reference.

Cc: Qian Cai <[email protected]>
Fixes: 1518ac272e78 ("vfio/pci: fix memory leaks of eventfd ctx")
Reported-by: Daniel Wagner <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Tested-by: Daniel Wagner <[email protected]>
Signed-off-by: Alex Williamson <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
[Lee: Remove references to non-existent 'req_trigger']
Signed-off-by: Lee Jones <[email protected]>
Change-Id: I9228a67dfdc5492547736dcac69995ad1883ab78

Author: Alex Williamson

drivers/vfio/pci/vfio_pci.c

@@ -181,8 +181,10 @@ static void vfio_pci_release(void *device_data)
 	if (!(--vdev->refcnt)) {
 		vfio_spapr_pci_eeh_release(vdev->pdev);
 		vfio_pci_disable(vdev);
-		if (vdev->err_trigger)
+		if (vdev->err_trigger) {
 			eventfd_ctx_put(vdev->err_trigger);
+			vdev->err_trigger = NULL;
+		}
 	}
 
 	mutex_unlock(&driver_lock);