static long ffs_epfile_ioctl(struct file *file, unsigned code,
			     unsigned long value)
{
	struct ffs_epfile *epfile = file->private_data;
	int ret;

	ENTER();

	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
		return -ENODEV;

	spin_lock_irq(&epfile->ffs->eps_lock);
	if (likely(epfile->ep)) {
		switch (code) {
		case FUNCTIONFS_FIFO_STATUS:
			ret = usb_ep_fifo_status(epfile->ep->ep);
			break;
		case FUNCTIONFS_FIFO_FLUSH:
			usb_ep_fifo_flush(epfile->ep->ep);
			ret = 0;
			break;
		case FUNCTIONFS_CLEAR_HALT:
			ret = usb_ep_clear_halt(epfile->ep->ep);
			break;
		case FUNCTIONFS_ENDPOINT_REVMAP:
			ret = epfile->ep->num;
			break;
		case FUNCTIONFS_ENDPOINT_DESC:
		{
			int desc_idx;
			struct usb_endpoint_descriptor *desc;

			switch (epfile->ffs->gadget->speed) {
			case USB_SPEED_SUPER:
				desc_idx = 2;
				break;
			case USB_SPEED_HIGH:
				desc_idx = 1;
				break;
			default:
				desc_idx = 0;
			}
			desc = epfile->ep->descs[desc_idx];

			spin_unlock_irq(&epfile->ffs->eps_lock);
			ret = copy_to_user((void *)value, desc, sizeof(*desc));
			if (ret)
				ret = -EFAULT;
			return ret;
		}
		default:
			ret = -ENOTTY;
		}
	} else {
		ret = -ENODEV;
	}
	spin_unlock_irq(&epfile->ffs->eps_lock);

	return ret;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.