The 31-year-old Senegal international has made five appearances for the Whites this season, all on a non-contract basis.
Neil Warnock has been keen to secure the former Liverpool forward on a more permanent basis, though, and he has now managed to do so, with the club confirming the news after Saturday afternoon's clash with Blackburn.
Warnock has been particularly vocal about a need for new bodies, with the proposed takeover of the club - a saga which has been ongoing since June - still to be resolved.
Chairman Ken Bates addressed the issue in his programme notes, writing: "There is a lot that goes on behind the scenes which unfortunately cannot be put into the public arena. I am determined that when I move on my legacy will be that the club is in safe hands."