[PATCH v2 2/3] powerpc/pseries: switch to dynamic ibmebus root device

[Johan Hovold <johan@kernel.org>]

Driver core expects devices to be dynamically allocated and will, for
example, complain loudly if a device that lacks a release function is
ever freed.

Use root_device_register() to allocate and register the root device
instead of open coding using a static device.

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

Signed-off-by: Johan Hovold <johan@kernel.org>
---
 arch/powerpc/platforms/pseries/ibmebus.c | 39 ++++++++++++++----------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/ibmebus.c b/arch/powerpc/platforms/pseries/ibmebus.c
index cad2deb7e70d..f2064e0b975d 100644
--- a/arch/powerpc/platforms/pseries/ibmebus.c
+++ b/arch/powerpc/platforms/pseries/ibmebus.c
@@ -51,9 +51,7 @@
 #include <asm/ibmebus.h>
 #include <asm/machdep.h>
 
-static struct device ibmebus_bus_device = { /* fake "parent" device */
-	.init_name = "ibmebus",
-};
+static struct device *ibmebus_bus_device;	/* fake "parent" device */
 
 const struct bus_type ibmebus_bus_type;
 
@@ -171,7 +169,10 @@ static int ibmebus_create_device(struct device_node *dn)
 	struct platform_device *dev;
 	int ret;
 
-	dev = of_device_alloc(dn, NULL, &ibmebus_bus_device);
+	if (!ibmebus_bus_device)
+		return -ENOENT;
+
+	dev = of_device_alloc(dn, NULL, ibmebus_bus_device);
 	if (!dev)
 		return -ENOMEM;
 
@@ -447,6 +448,7 @@ EXPORT_SYMBOL(ibmebus_bus_type);
 
 static int __init ibmebus_bus_init(void)
 {
+	struct device *root;
 	int err;
 
 	printk(KERN_INFO "IBM eBus Device Driver\n");
@@ -458,23 +460,28 @@ static int __init ibmebus_bus_init(void)
 		return err;
 	}
 
-	err = device_register(&ibmebus_bus_device);
-	if (err) {
-		printk(KERN_WARNING "%s: device_register returned %i\n",
+	root = root_device_register("ibmebus");
+	if (IS_ERR(root)) {
+		err = PTR_ERR(root);
+		printk(KERN_WARNING "%s: root_device_register returned %i\n",
 		       __func__, err);
-		put_device(&ibmebus_bus_device);
-		bus_unregister(&ibmebus_bus_type);
-
-		return err;
+		goto err_deregister_bus;
 	}
 
+	ibmebus_bus_device = root;
+
 	err = ibmebus_create_devices(ibmebus_matches);
-	if (err) {
-		device_unregister(&ibmebus_bus_device);
-		bus_unregister(&ibmebus_bus_type);
-		return err;
-	}
+	if (err)
+		goto err_deregister_root;
 
 	return 0;
+
+err_deregister_root:
+	ibmebus_bus_device = NULL;
+	root_device_unregister(root);
+err_deregister_bus:
+	bus_unregister(&ibmebus_bus_type);
+
+	return err;
 }
 machine_postcore_initcall(pseries, ibmebus_bus_init);
-- 
2.53.0