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 %sn”,
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.
