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    Subject[PATCH 1/5] 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>
    ---
    drivers/uio/uio.c | 58 +++++++++++++---------------------------------------
    1 files changed, 15 insertions(+), 43 deletions(-)

    diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
    index bff1afb..bc774cc 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)
    --
    1.7.2.2


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