To be honest mate, might sound a bit naughty but if your using it for a portfolio or just to show your friends/prospective employers I wouldnt worry about it, even if you put it on youtube, its unlikely if the artist of the song will come after you over a personal project, if they do all they will probably do is ask you to remove it, might be flying colse to the wind but I really doubt you'll have a problem, if your going to ask for money then you would need to look getting a licence for it.
BUT onto the question, I think that whoever performs the cover has to get the permission form the original artist, or whoever owns the licence (dunno but as Michael Jackson owns a lot of the beatles stuff Paul McCartney would need his permission to perform it, strange as that might seem) bands get away with it in pub's/clubs as the venue has a licence to allow the performance (or playing any music I think).
"No pressure, no diamonds" Thomas Carlyle