In the Linux kernel, the following vulnerability has been resolved: usb: gadget: goku_udc: avoid...

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: goku_udc: avoid NULL deref of dev->driver in INT_USBRESET log

goku_irq() handles a number of bus events under a single ep0 path. It already guards the gadget driver suspend/resume callbacks against a NULL ->driver:

if (dev->gadget.speed != USB_SPEED_UNKNOWN
		&& dev->driver
		&& dev->driver->resume) {
	spin_unlock(&dev->lock);
	dev->driver->resume(&dev->gadget);
	...
}

but the very next branch unconditionally dereferences dev->driver when an INT_USBRESET arrives:

if (stat & INT_USBRESET) {
	ACK(INT_USBRESET);
	INFO(dev, "USB reset done, gadget %s\n",
		dev->driver->driver.name);
}

If the controller raises INT_USBRESET before any gadget driver has been bound (or after one has been unbound), dev->driver is NULL and the printk dereferences NULL.

smatch flags the inconsistency:

drivers/usb/gadget/udc/goku_udc.c:1618 goku_irq() error: we previously assumed 'dev->driver' could be null (see line 1607)

Fall back to a placeholder when the gadget driver is not bound.

No functional change while a gadget driver is bound.