The IOUSBControllerUserClient::ReadRegister function in the IOUSB controller in IOUSBFamily in Apple OS X before 10.10.2 allows local users to read data from arbitrary kernel-memory locations by leveraging root access and providing a crafted first argument.
http://code.google.com/p/google-security-research/issues/detail?id=21
http://lists.apple.com/archives/security-announce/2015/Jan/msg00003.html
http://support.apple.com/HT204244