What is the rule regarding drivers a lap down overtaking drivers fighting at the top?

Is what Kubica did in the final lap legal overtaking-wise?

Another separate point - is his driving at that corner reckless?
thank u for the replies. what i'm really interested in is... what does the f1 guidelines/code say? when do they slap a penalty when they think that the driver a lap down is holding up those in front?

do they use telemetry, subjective opinion or something else?

1. no way, that is just Kubica saying, screw it l got nothing to lose, so let is wreck everyone else is season.

2. Not really, it is what some drivers do also most notably Hamilton, Alonso, and Raikonnen.

It has happened in the past. l remember Eddie Irvine un-lapping himself from Ayrton Senna. After the race it is said the Senna punched him in the mouth lol. l do not think it is illegal if the lead car is moving slower.

Its ok for a driver to unlap himself but they are not allowed to hold people up by being in front of a faster car.
He did not break the rules.

kubica = vettel over take lewis = traffic = glock lost in on dry = championship

l do not think it was reckless, l do think it was unnecessary for him to challenge one of the title contenders when he was a lap down. If Massa won the title, l am sure there would have been some sort of investigation and enquiry.