[libvirt] Potential segfault in udev driver

udevDeviceMonitorStartup registers udevEventHandleCallback as event handle, but doesn't store the returned watch id to remove it later on. Also it's not clear to me whether the event handle should be register for the whole lifetime of the udev driver instance or just for the udevEnumerateDevices call. If for example the call to udevSetupSystemDev [1] fails udevDeviceMonitorShutdown is called to cleanup, but udevEventHandleCallback is still registered and may be called when driverState is NULL again, resulting in a segfault in udevEventHandleCallback. So to solve this the udevEventHandleCallback event handle must be removed at the appropriate place. Maximilian Wilhelm found this problem. [1] 22:42:20.960: error : udevSetupSystemDev:1460 : Failed to get udev device for syspath '/sys/devices/virtual/dmi/id' or '/sys/class/dmi/id' Matthias