Internet of things (IoT) paradigm poses new challenges to the communication technology as numerous heterogeneous objects will need to be connected. To address these issues new radio technologies and network architectures need to be designed to cater to several future devices having connectivity demands. For radio communications, the frequency spectrum allocation will have to be adapted for efficient spectrum utilization considering new bandwidth and application requirements. Novel research directions based on the use of opportunistic radio resource utilization such as those based on cognitive radio (CR) technology will have to be pursued for efficiency as well as reliability. Cognitive Radio is a promising enabler communication technology for IoT. Its opportunistic communication paradigm is suited to communicating objects having event driven nature, that generate bursty traffic. Cognitive Radio can help overcome the problems of collision and excessive contention in the wireless access network that will arise due to the deployment of several objects connected to infrastructure through radio links. However, there are several issues that need to be addressed before cognitive radio technology can be used for Internet of things. This paper surveys novel approaches and discusses research challenges related to the use of cognitive radio technology for Internet of things. In addition, the paper presents a general background on cognitive radio and Internet of Things with some potential applications. Our survey is different from existing surveys in that we focus on recent advances and ongoing research directions in cognitive radio in the context of Machine to Machine and Internet of Things. We review CR solutions that address generic problems of IoT including emerging challenges of autonomicity, scalability, energy efficiency, heterogeneity in terms of user equipment capabilities, complexity and environments, etc. The solutions are supported by our taxonomy of different CR approaches that are classified into two categories, flexible and efficient networking, and tackling heterogeneity. This paper intends to help new researchers entering the domain of CR and IoT by providing a comprehensive survey on recent advances.