Where there genocides or concentration camps in Russia or Eastern Europe after WWII?

Oh Lord yes. In Russia the "re-education" camps were called "gulags." The Russian author Alexander Solshenityn broke on to the world literary scene in the early 1960s with a novel calleld "One Day In The Life of Ivan Denisovich." The author was in a unique position to write this gripping novel about life in the gulags, as he had spent several years there for the usual crime -- offending the authorities.