"He's been given the all-clear (by Suntory) to complete the rest of the season for us," a club spokesman said.
Smith's contract extension is likely to clear his way back into the frame for Wallabies selection ahead of the British and Irish Lions tour in June and July.
Smith's rampaging form with the Canberra-based Brumbies on a short-term contract in the southern hemisphere competition, coupled with the loss of incumbent openside flanker David Pocock, has propelled the 110-cap Wallaby into selection discussions, despite his ineligibility to play for Australia.
Australia coach Robbie Deans told Reuters last month that he would consider Smith for selection if he became eligible.
"This has been a special opportunity for me and my family, to return to the Brumbies for what will probably be the last time," Smith said of the contract extension.
"I've already been lucky enough to build a legacy I am proud of with the club, so to be given another chance to add to that is exciting."
If Smith were to make the Wallabies team for the three matches against the Lions in June and July, he would be facing the tourists in a second series having played in all three of the matches in Australia's 2-1 win in 2001.
Smith's selection would trample on the Australian Rugby Union's usual practice of ruling out internationally-contracted players for Wallabies duties, but would be a price worth paying, according to Australia loose forward Dave Dennis.
"If he's around and he's selected it's obviously going to add a lot of value to the squad so I don't think there will be too many complaints if he's in that squad," Dennis told Reuters.
- Sports & Recreation