In the Linux kernel, the following vulnerability has been resolved: usb: gadget: goku_udc: avoid NULL deref of dev->driver in INT_USBRESET

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:

 1if (dev->gadget.speed != USB_SPEED_UNKNOWN
 2		&& dev->driver
 3		&& dev->driver->resume) {
 4	spin_unlock(&dev->lock);
 5	dev->driver->resume(&dev->gadget);
 6	...
 7}

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

 1if (stat & INT_USBRESET) {
 2	ACK(INT_USBRESET);
 3	INFO(dev, "USB reset done, gadget %s\n",
 4		dev->driver->driver.name);
 5}

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.