Linux Driver Verification » Linux Kernel Safety RuleDB

Proper reference counting should be performed for struct usb_device with the use of functions usb_get_dev/usb_put_dev.

/**
 * usb_get_dev - increments the reference count of the usb device structure
 * @dev: the device being referenced
 *
 * Each live reference to a device should be refcounted.
 *
 * Drivers for USB interfaces should normally record such references in
 * their probe() methods, when they bind to an interface, and release
 * them by calling usb_put_dev(), in their disconnect() methods.

Usually the reference count is increased in probe() handler and decreased in disconnect()/exit() handler. It look like interface_to_usbdev() macro is often used in probe() handler to get the reference to usb_device by the reference to usb_interface.

So the rule may be initially formalized in the following way: after acquiring a reference to struct usb_device with usb_interface macro one should increase the corresponding reference counter with usb_get_dev and then decrease it with usb_put_dev at finalization.

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Sample bugfixes 927c3fa