static int ffs_func_setup(struct usb_function *f,
			  const struct usb_ctrlrequest *creq)
{
	struct ffs_function *func = ffs_func_from_usb(f);
	struct ffs_data *ffs = func->ffs;
	unsigned long flags;
	int ret;

	ENTER();

	pr_vdebug("creq->bRequestType = %02x\n", creq->bRequestType);
	pr_vdebug("creq->bRequest     = %02x\n", creq->bRequest);
	pr_vdebug("creq->wValue       = %04x\n", le16_to_cpu(creq->wValue));
	pr_vdebug("creq->wIndex       = %04x\n", le16_to_cpu(creq->wIndex));
	pr_vdebug("creq->wLength      = %04x\n", le16_to_cpu(creq->wLength));

	/*
	 * Most requests directed to interface go through here
	 * (notable exceptions are set/get interface) so we need to
	 * handle them.  All other either handled by composite or
	 * passed to usb_configuration->setup() (if one is set).  No
	 * matter, we will handle requests directed to endpoint here
	 * as well (as it's straightforward) but what to do with any
	 * other request?
	 */
	if (ffs->state != FFS_ACTIVE)
		return -ENODEV;

	switch (creq->bRequestType & USB_RECIP_MASK) {
	case USB_RECIP_INTERFACE:
		ret = ffs_func_revmap_intf(func, le16_to_cpu(creq->wIndex));
		if (unlikely(ret < 0))
			return ret;
		break;

	case USB_RECIP_ENDPOINT:
		ret = ffs_func_revmap_ep(func, le16_to_cpu(creq->wIndex));
		if (unlikely(ret < 0))
			return ret;
		if (func->ffs->user_flags & FUNCTIONFS_VIRTUAL_ADDR)
			ret = func->ffs->eps_addrmap[ret];
		break;

	default:
		return -EOPNOTSUPP;
	}

	spin_lock_irqsave(&ffs->ev.waitq.lock, flags);
	ffs->ev.setup = *creq;
	ffs->ev.setup.wIndex = cpu_to_le16(ret);
	__ffs_event_add(ffs, FUNCTIONFS_SETUP);
	spin_unlock_irqrestore(&ffs->ev.waitq.lock, flags);

	return 0;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.