Linux kernel module usb filter example with userspace control application

usb_filter.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/usb.h>

#define USB_FILTER_ADD_DEVICE _IO('u', 0)
#define USB_FILTER_REMOVE_DEVICE _IO('u', 1)

static int is_device_blacklisted(struct usb_device *dev) {
    // Check if the device is blacklisted based on some criteria
    return 0; // Return 1 if blacklisted, 0 otherwise
}

static long usb_filter_ioctl(struct file *file, unsigned int cmd, unsigned long arg) {
    struct usb_device *dev;
    int result;

    switch (cmd) {
        case USB_FILTER_ADD_DEVICE:
            dev = (struct usb_device *)arg;
            result = is_device_blacklisted(dev);
            if (result) {
                printk(KERN_INFO "USB device (%04X:%04X) is already blacklisted\n",
                    le16_to_cpu(dev->descriptor.idVendor),
                    le16_to_cpu(dev->descriptor.idProduct));
            } else {
                // Add the device to the blacklist
                printk(KERN_INFO "Added USB device (%04X:%04X) to the blacklist\n",
                    le16_to_cpu(dev->descriptor.idVendor),
                    le16_to_cpu(dev->descriptor.idProduct));
            }
            break;

        case USB_FILTER_REMOVE_DEVICE:
            dev = (struct usb_device *)arg;
            result = is_device_blacklisted(dev);
            if (result) {
                // Remove the device from the blacklist
                printk(KERN_INFO "Removed USB device (%04X:%04X) from the blacklist\n",
                    le16_to_cpu(dev->descriptor.idVendor),
                    le16_to_cpu(dev->descriptor.idProduct));
            } else {
                printk(KERN_INFO "USB device (%04X:%04X) is not blacklisted\n",
                    le16_to_cpu(dev->descriptor.idVendor),
                    le16_to_cpu(dev->descriptor.idProduct));
            }
            break;

        default:
            return -EINVAL;
    }

    return 0;
}

static struct file_operations usb_filter_fops = {
    .owner = THIS_MODULE,
    .unlocked_ioctl = usb_filter_ioctl,
};

static int __init usb_filter_init(void) {
    // Register the USB filter module
    // ...

    return 0;
}

static void __exit usb_filter_exit(void) {
    // Unregister the USB filter module
    // ...
}

module_init(usb_filter_init);
module_exit(usb_filter_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("USB filter kernel module");

usbfilterapp.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/usb.h>

#define USB_FILTER_ADD_DEVICE _IO('u', 0)
#define USB_FILTER_REMOVE_DEVICE _IO('u', 1)

int main() {
    int fd;
    struct usb_device dev;

    fd = open("/dev/usb_filter", O_RDWR);
    if (fd < 0) {
        perror("Failed to open /dev/usb_filter");
        return EXIT_FAILURE;
    }

    // Add a device to the blacklist
    if (ioctl(fd, USB_FILTER_ADD_DEVICE, &dev) < 0) {
        perror("Failed to add device to the blacklist");
        close(fd);
        return EXIT_FAILURE;
    }

    // Remove a device from the blacklist
    if (ioctl(fd, USB_FILTER_REMOVE_DEVICE, &dev) < 0) {
        perror("Failed to remove device from the blacklist");
        close(fd);
        return EXIT_FAILURE;
    }

    close(fd);