driver core: faux: fix root device registration

A recent change made the faux bus root device be allocated dynamically but failed to provide a release function to free the memory when the last reference is dropped (on theoretical failure to register the device or bus).

Fix this by using root_device_register() instead of open coding.

Also add the missing sanity check when registering faux devices to avoid a NULL-pointer dereference if the bus failed to register (which would previously have triggered a bunch of use-after-free warnings).

drivers/base/faux.c +5 -12

+
 	faux_obj = kzalloc_obj(*faux_obj);
 	if (!faux_obj)
 		return NULL;

@@ -234,17 +237,9 @@ int __init faux_bus_init(void)
 {
 	int ret;
 
-	faux_bus_root = kzalloc_obj(*faux_bus_root);
-	if (!faux_bus_root)
-		return -ENOMEM;
-
-	dev_set_name(faux_bus_root, "faux");
-
-	ret = device_register(faux_bus_root);
-	if (ret) {
-		put_device(faux_bus_root);
-		return ret;
-	}
+	faux_bus_root = root_device_register("faux");
+	if (IS_ERR(faux_bus_root))
+		return PTR_ERR(faux_bus_root);
 
 	ret = bus_register(&faux_bus_type);
 	if (ret)

@@ -260,6 +255,6 @@ int __init faux_bus_init(void)
 	bus_unregister(&faux_bus_type);
 
 error_bus:
-	device_unregister(faux_bus_root);
+	root_device_unregister(faux_bus_root);
 	return ret;
 }

Signature · 1 line

2.53.0

drivers/base/faux.c struct faux_device *faux_device_create_with_groups(const char *name, · line 137

Quoted 10 lines · Johan Hovold

drivers/base/faux.c +2 -0

index fb3e42f21362..402ed119dfdf 100644
@@ -133,6 +133,9 @@ struct faux_device *faux_device_create_with_groups(const char *name,
 	struct device *dev;
 	int ret;
 
+	if (IS_ERR_OR_NULL(faux_bus_root))
+		return NULL;

As Greg mentioned, if this happens we already have a much bigger fundamental problem earlier in the boot process.

Anyway, I think this check only catches when root_device_register() fails, but everything that comes after root_device_register() in faux_bus_init() still leaves us with a dangling pointer.