uio: Fix lack of locking in init_uio_class

There is no locking in init_uio_class so multiple
drivers can race and create multiple uio classes.

Fix this by simplifying the code.   In particular always
register the uio class during module_init and make things
simpler.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Hans J. Koch <hjk@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 15 insertions, 43 deletions

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index bff1afbde5a4..bc774cce0a4d 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -45,10 +45,7 @@ static DEFINE_IDR(uio_idr);
 static const struct file_operations uio_fops;
 
 /* UIO class infrastructure */
-static struct uio_class {
-        struct kref kref;
-        struct class *class;
-} *uio_class;
+static struct class *uio_class;
 
 /* Protect idr accesses */
 static DEFINE_MUTEX(minor_lock);
@@ -757,55 +754,35 @@ static void uio_major_cleanup(void)
 
 static int init_uio_class(void)
 {
-        int ret = 0;
-
-        if (uio_class != NULL) {
-                kref_get(&uio_class->kref);
-                goto exit;
-        }
+        struct class *class;
+        int ret;
 
         /* This is the first time in here, set everything up properly */
         ret = uio_major_init();
         if (ret)
                 goto exit;
 
-        uio_class = kzalloc(sizeof(*uio_class), GFP_KERNEL);
-        if (!uio_class) {
-                ret = -ENOMEM;
-                goto err_kzalloc;
-        }
-
-        kref_init(&uio_class->kref);
-        uio_class->class = class_create(THIS_MODULE, "uio");
-        if (IS_ERR(uio_class->class)) {
-                ret = IS_ERR(uio_class->class);
+        class = class_create(THIS_MODULE, "uio");
+        if (IS_ERR(class)) {
+                ret = IS_ERR(class);
                 printk(KERN_ERR "class_create failed for uio\n");
                 goto err_class_create;
         }
+        uio_class = class;
         return 0;
 
 err_class_create:
-        kfree(uio_class);
-        uio_class = NULL;
-err_kzalloc:
         uio_major_cleanup();
 exit:
         return ret;
 }
 
-static void release_uio_class(struct kref *kref)
+static void release_uio_class(void)
 {
         /* Ok, we cheat as we know we only have one uio_class */
-        class_destroy(uio_class->class);
-        kfree(uio_class);
-        uio_major_cleanup();
+        class_destroy(uio_class);
         uio_class = NULL;
-}
-
-static void uio_class_destroy(void)
-{
-        if (uio_class)
-                kref_put(&uio_class->kref, release_uio_class);
+        uio_major_cleanup();
 }
 
 /**
@@ -828,10 +805,6 @@ int __uio_register_device(struct module *owner,
 
         info->uio_dev = NULL;
 
-        ret = init_uio_class();
-        if (ret)
-                return ret;
-
         idev = kzalloc(sizeof(*idev), GFP_KERNEL);
         if (!idev) {
                 ret = -ENOMEM;
@@ -847,7 +820,7 @@ int __uio_register_device(struct module *owner,
         if (ret)
                 goto err_get_minor;
 
-        idev->dev = device_create(uio_class->class, parent,
+        idev->dev = device_create(uio_class, parent,
                                   MKDEV(uio_major, idev->minor), idev,
                                   "uio%d", idev->minor);
         if (IS_ERR(idev->dev)) {
@@ -874,13 +847,12 @@ int __uio_register_device(struct module *owner,
 err_request_irq:
         uio_dev_del_attributes(idev);
 err_uio_dev_add_attributes:
-        device_destroy(uio_class->class, MKDEV(uio_major, idev->minor));
+        device_destroy(uio_class, MKDEV(uio_major, idev->minor));
 err_device_create:
         uio_free_minor(idev);
 err_get_minor:
         kfree(idev);
 err_kzalloc:
-        uio_class_destroy();
         return ret;
 }
 EXPORT_SYMBOL_GPL(__uio_register_device);
@@ -907,9 +879,8 @@ void uio_unregister_device(struct uio_info *info)
         uio_dev_del_attributes(idev);
 
         dev_set_drvdata(idev->dev, NULL);
-        device_destroy(uio_class->class, MKDEV(uio_major, idev->minor));
+        device_destroy(uio_class, MKDEV(uio_major, idev->minor));
         kfree(idev);
-        uio_class_destroy();
 
         return;
 }
@@ -917,11 +888,12 @@ EXPORT_SYMBOL_GPL(uio_unregister_device);
 
 static int __init uio_init(void)
 {
-        return 0;
+        return init_uio_class();
 }
 
 static void __exit uio_exit(void)
 {
+        release_uio_class();
 }
 
 module_init(uio_init)