drm/i915: Remove pci private pointer after destroying the device private

On an aborted module load, we unwind and free our device private - but
we left a dangling pointer to our privates inside the pci_device. After
the attempted aborted unload, we may still get a call to i915_pci_remove()
when the module is removed, potentially chasing stale data.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180716080332.32283-5-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.c

@@ -1424,6 +1424,7 @@ out_fini:
 	drm_dev_fini(&dev_priv->drm);
 out_free:
 	kfree(dev_priv);
+	pci_set_drvdata(pdev, NULL);
 	return ret;
 }
 

drivers/gpu/drm/i915/i915_pci.c

@@ -674,10 +674,16 @@ MODULE_DEVICE_TABLE(pci, pciidlist);
 
 static void i915_pci_remove(struct pci_dev *pdev)
 {
-	struct drm_device *dev = pci_get_drvdata(pdev);
+	struct drm_device *dev;
+
+	dev = pci_get_drvdata(pdev);
+	if (!dev) /* driver load aborted, nothing to cleanup */
+		return;
 
 	i915_driver_unload(dev);
 	drm_dev_put(dev);
+
+	pci_set_drvdata(pdev, NULL);
 }
 
 static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
@@ -712,6 +718,11 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (err)
 		return err;
 
+	if (i915_inject_load_failure()) {
+		i915_pci_remove(pdev);
+		return -ENODEV;
+	}
+
 	err = i915_live_selftests(pdev);
 	if (err) {
 		i915_pci_remove(pdev);