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>

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index bff1afb..bc774cc 100644 (file)
--- 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)