Linux Arbitary RAM Access Kernel Module (not working well)

#include <linux/module.h>
#include <linux/version.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cdev.h>

static dev_t first;
static struct cdev c_dev;
static struct class *cl;

static int dopen(struct inode *i,struct file *f)
{
    printk(KERN_INFO "Driver: open()\n");
    return 0;
}

static int dclose(struct inode *i,struct file *f)
{
    printk(KERN_INFO "Driver: close()\n");
    return 0;
}

static ssize_t dread(struct file *f,char __user *buf,size_t len,loff_t *off)
{
    printk(KERN_INFO "Driver: read()\n");
    memcpy(buf,off,len);
    return len;
}

static ssize_t dwrite(struct file *f,const char __user *buf,size_t len,loff_t *off)
{
    printk(KERN_INFO "Driver: write()\n");
    memcpy(off,buf,len);
    return len;
}
static int duevent(struct device *dev,struct kobj_uevent_env *env)
{
    printk(KERN_INFO "Driver: uevent()\n");
    add_uevent_var(env,"DEVMODE=%#o",0666);
    return 0;
}

static struct file_operations pugs_fops=
{
    .owner=THIS_MODULE,
    .open=dopen,
    .release=dclose,
    .read=dread,
    .write=dwrite,
};

static int __init benarydev_init(void)
{
    printk(KERN_INFO "benarydev: starting");
    if(alloc_chrdev_region(&first,0,1,"benarydev")<0)
    {
        return -1;
    }
    if ((cl = class_create(THIS_MODULE,"chardrv")) == NULL)
    {
        unregister_chrdev_region(first,1);
        return -1;
    }
    cl->dev_uevent=duevent;
    if (device_create(cl,NULL,first,NULL,"benarydevnull") == NULL)
    {
        class_destroy(cl);
        unregister_chrdev_region(first,1);
        return -1;
    }
    cdev_init(&c_dev,&pugs_fops);
    if (cdev_add(&c_dev,first,1) == -1)
    {
        device_destroy(cl,first);
        class_destroy(cl);
        unregister_chrdev_region(first,1);
        return -1;
    }
    printk(KERN_INFO "benarydev: started");
    return 0;
}

static void __exit benarydev_exit(void)
{
    printk(KERN_INFO "benarydev: stopping");
    cdev_del(&c_dev);
    device_destroy(cl, first);
    class_destroy(cl);
    unregister_chrdev_region(first, 1);
    printk(KERN_INFO "benarydev: stopped");
}

module_init(benarydev_init);
module_exit(benarydev_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("benaryorg <binary at benary dot org>");
MODULE_DESCRIPTION("benaryorg's device driver");