Pornography was illegal in the USSR. Possession could get up to 3 years in prison, or a 300 ruble fine (which was low enough for most people to be able to scrape together enough to stay out of prison).
Soviet social morals were pretty strict, and expressions of sexuality in art were virtually non-existent, at least overtly. It wasn’t until 1988 with the film ‘Malenkaya Vera’ that a sex scene was shown in the cinema. Of course, love stories did exist in huge numbers, and were very popular in music, film, and art -they were just based on romantic innocent conceptions of love rather than on sex. Naturalist art forms such as paintings and sculpture were also approved -once again just not with sexual contexts.