Official WC playoff rules

Playoff rules:

3.7.1.a If the scores are level after the regular twelve (12) games, after a new drawing of colors, four (4) tie-break games shall be played. The games shall be played using the electronic clock starting with 25 minutes for each player with an increment of 10 seconds after each move.

3.7.2 If the scores are level after the games in Article 3.7.1a, then, after a new drawing of colors, a match of 2 games shall be played with a time control of 5 minutes plus 3 seconds increment after each move. In case of a level score, another 2-game match will be played to determine a winner. If still there is no winner after 5 such matches (total 10 games), one sudden-death game will be played as described below in Article 3.7.3.

3.7.3 If the score is still level after five matches as described in Article 3.7.2, the players shall play a one sudden death game. The player who wins the drawing of lots may choose the color. The player with the white pieces shall receive 5 minutes, the player with the black pieces shall receive 4 minutes whereupon, after the 60th move, both players shall receive an increment of 3 seconds from move 61. In case of a draw the player with the black pieces is declared the winner.

Full details here: http://moscow2012.fide.com/files/FWCM2012.pdf