/* * faulty.c -- a module which generates an oops when read * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files.  The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates.   No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * $Id: faulty.c,v 1.3 2004/09/26 07:02:43 gregkh Exp $ */#include <linux/config.h>#include <linux/module.h>#include <linux/init.h>#include <linux/kernel.h> /* printk() */#include <linux/fs.h>     /* everything... */#include <linux/types.h>  /* size_t */#include <asm/uaccess.h>MODULE_LICENSE("Dual BSD/GPL");int faulty_major = 0;ssize_t faulty_read(struct file *filp, char __user *buf,		    size_t count, loff_t *pos){	int ret;	char stack_buf[4];	/* Let's try a buffer overflow  */	memset(stack_buf, 0xff, 20);	if (count > 4)		count = 4; /* copy 4 bytes to the user */	ret = copy_to_user(buf, stack_buf, count);	if (!ret)		return count;	return ret;}ssize_t faulty_write (struct file *filp, const char __user *buf, size_t count,		loff_t *pos){	/* make a simple fault by dereferencing a NULL pointer */	*(int *)0 = 0;	return 0;}struct file_operations faulty_fops = {	.read =  faulty_read,	.write = faulty_write,	.owner = THIS_MODULE};int faulty_init(void){	int result;	/*	 * Register your major, and accept a dynamic number	 */	result = register_chrdev(faulty_major, "faulty", &faulty_fops);	if (result < 0)		return result;	if (faulty_major == 0)		faulty_major = result; /* dynamic */	return 0;}void faulty_cleanup(void){	unregister_chrdev(faulty_major, "faulty");}module_init(faulty_init);module_exit(faulty_cleanup);