The oxygen vacancy, interstitial oxygen and hafnium, hafnium substituting oxygen and oxygen Frenkel pair in HfO2 are the probable defects which are able to participate in the conducting filament formation in hafnia-based RRAM. In this paper, we studied the atomic and electronic structures of above-listed defects within the first principles simulation. It was found that all studied defects can be involved in the charge transport. Oxygen vacancies are the key defects for the charge transport and RRAM operability. It was suggested that interstitial oxygen atoms make a significant contribution to the HfO2 hole conductivity. The hafnium interstitial competes with an oxygen interstitial and the Frenkel pair in the conducting filament formation in O-poor conditions. The oxygen vacancies and hafnium substituting oxygen pairs atomic structure indicate a tendency to these defects clustering.