vuln-mod.c

/*

Author: Marcin Kozlowski <marcinguy@gmail.com>

*/


#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>
#include <linux/uaccess.h>

struct proc_dir_entry *proc_file_entry;

// Buggy write handling
static ssize_t buggy_write(struct file *file,const char *buf, size_t len, loff_t *off){

        
        char data[4];

        printk("buggy_write %s %i", buf, len);
        __copy_from_user(&data, buf,len);

        return len;
}

static const struct file_operations proc_file_fops = {
 .owner = THIS_MODULE,
 .write  = buggy_write
};

int init_module()  
{
        printk("module started");
        printk("creating proc entry @ /proc/buggy");

        // handle anything written to /proc/buggy
        // pass it to buggy_write
        proc_file_entry = proc_create_data("buggy", 0666, NULL, &proc_file_fops,NULL);

        return 0;
}

void cleanup_module()  
{
        remove_proc_entry("buggy", NULL);
}