PCI: use generic driver_override infrastructure

When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]

Link: https://lore.kernel.org/driver-core/[email protected]/ [1]
Reported-by: Gui-Dong Han <[email protected]>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: 782a985 ("PCI: Introduce new device binding path using pci_dev.driver_override")
Acked-by: Bjorn Helgaas <[email protected]>
Acked-by: Alex Williamson <[email protected]>
Tested-by: Gui-Dong Han <[email protected]>
Reviewed-by: Gui-Dong Han <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Danilo Krummrich <[email protected]>

Author: Danilo Krummrich

drivers/pci/pci-driver.c

@@ -138,9 +138,11 @@ static const struct pci_device_id *pci_match_device(struct pci_driver *drv,
 {
 	struct pci_dynid *dynid;
 	const struct pci_device_id *found_id = NULL, *ids;
+	int ret;
 
 	/* When driver_override is set, only bind to the matching driver */
-	if (dev->driver_override && strcmp(dev->driver_override, drv->name))
+	ret = device_match_driver_override(&dev->dev, &drv->driver);
+	if (ret == 0)
 		return NULL;
 
 	/* Look at the dynamic ids first, before the static ones */
@@ -164,15 +166,15 @@ static const struct pci_device_id *pci_match_device(struct pci_driver *drv,
 		 * matching.
 		 */
 		if (found_id->override_only) {
-			if (dev->driver_override)
+			if (ret > 0)
 				return found_id;
 		} else {
 			return found_id;
 		}
 	}
 
 	/* driver_override will always match, send a dummy id */
-	if (dev->driver_override)
+	if (ret > 0)
 		return &pci_device_id_any;
 	return NULL;
 }
@@ -452,7 +454,7 @@ static int __pci_device_probe(struct pci_driver *drv, struct pci_dev *pci_dev)
 static inline bool pci_device_can_probe(struct pci_dev *pdev)
 {
 	return (!pdev->is_virtfn || pdev->physfn->sriov->drivers_autoprobe ||
-		pdev->driver_override);
+		device_has_driver_override(&pdev->dev));
 }
 #else
 static inline bool pci_device_can_probe(struct pci_dev *pdev)
@@ -1722,6 +1724,7 @@ static const struct cpumask *pci_device_irq_get_affinity(struct device *dev,
 
 const struct bus_type pci_bus_type = {
 	.name		= "pci",
+	.driver_override = true,
 	.match		= pci_bus_match,
 	.uevent		= pci_uevent,
 	.probe		= pci_device_probe,

drivers/pci/pci-sysfs.c

@@ -615,33 +615,6 @@ static ssize_t devspec_show(struct device *dev,
 static DEVICE_ATTR_RO(devspec);
 #endif
 
-static ssize_t driver_override_store(struct device *dev,
-				     struct device_attribute *attr,
-				     const char *buf, size_t count)
-{
-	struct pci_dev *pdev = to_pci_dev(dev);
-	int ret;
-
-	ret = driver_set_override(dev, &pdev->driver_override, buf, count);
-	if (ret)
-		return ret;
-
-	return count;
-}
-
-static ssize_t driver_override_show(struct device *dev,
-				    struct device_attribute *attr, char *buf)
-{
-	struct pci_dev *pdev = to_pci_dev(dev);
-	ssize_t len;
-
-	device_lock(dev);
-	len = sysfs_emit(buf, "%s\n", pdev->driver_override);
-	device_unlock(dev);
-	return len;
-}
-static DEVICE_ATTR_RW(driver_override);
-
 static struct attribute *pci_dev_attrs[] = {
 	&dev_attr_power_state.attr,
 	&dev_attr_resource.attr,
@@ -669,7 +642,6 @@ static struct attribute *pci_dev_attrs[] = {
 #ifdef CONFIG_OF
 	&dev_attr_devspec.attr,
 #endif
-	&dev_attr_driver_override.attr,
 	&dev_attr_ari_enabled.attr,
 	NULL,
 };

drivers/pci/probe.c

@@ -2488,7 +2488,6 @@ static void pci_release_dev(struct device *dev)
 	pci_release_of_node(pci_dev);
 	pcibios_release_device(pci_dev);
 	pci_bus_put(pci_dev->bus);
-	kfree(pci_dev->driver_override);
 	bitmap_free(pci_dev->dma_alias_mask);
 	dev_dbg(dev, "device released\n");
 	kfree(pci_dev);

drivers/vfio/pci/vfio_pci_core.c

@@ -1987,9 +1987,8 @@ static int vfio_pci_bus_notifier(struct notifier_block *nb,
 	    pdev->is_virtfn && physfn == vdev->pdev) {
 		pci_info(vdev->pdev, "Captured SR-IOV VF %s driver_override\n",
 			 pci_name(pdev));
-		pdev->driver_override = kasprintf(GFP_KERNEL, "%s",
-						  vdev->vdev.ops->name);
-		WARN_ON(!pdev->driver_override);
+		WARN_ON(device_set_driver_override(&pdev->dev,
+						   vdev->vdev.ops->name));
 	} else if (action == BUS_NOTIFY_BOUND_DRIVER &&
 		   pdev->is_virtfn && physfn == vdev->pdev) {
 		struct pci_driver *drv = pci_dev_driver(pdev);

drivers/xen/xen-pciback/pci_stub.c

@@ -598,6 +598,8 @@ static int pcistub_seize(struct pci_dev *dev,
 	return err;
 }
 
+static struct pci_driver xen_pcibk_pci_driver;
+
 /* Called when 'bind'. This means we must _NOT_ call pci_reset_function or
  * other functions that take the sysfs lock. */
 static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
@@ -609,8 +611,8 @@ static int pcistub_probe(struct pci_dev *dev, const struct pci_device_id *id)
 
 	match = pcistub_match(dev);
 
-	if ((dev->driver_override &&
-	     !strcmp(dev->driver_override, PCISTUB_DRIVER_NAME)) ||
+	if (device_match_driver_override(&dev->dev,
+					 &xen_pcibk_pci_driver.driver) > 0 ||
 	    match) {
 
 		if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL

include/linux/pci.h

@@ -575,12 +575,6 @@ struct pci_dev {
 	u8		supported_speeds; /* Supported Link Speeds Vector */
 	phys_addr_t	rom;		/* Physical address if not from BAR */
 	size_t		romlen;		/* Length if not from BAR */
-	/*
-	 * Driver name to force a match.  Do not set directly, because core
-	 * frees it.  Use driver_set_override() to set or clear it.
-	 */
-	const char	*driver_override;
-
 	unsigned long	priv_flags;	/* Private flags for the PCI driver */
 
 	/* These methods index pci_reset_fn_methods[] */