No, the entire movie is fiction based on the book "The 120 Days of Sodom" by Marquis de Sade.
The only part that is accurate is that there was a Nazi-backed puppet state set up in Italy from 1943-1945. The events in the film take place in 1944.
Pier Paolo Pasolini lived through that era and lost his brother during it, which is why he took the events from the
Marquis de Sade's novel The 120 Days of Sodom, originally written in France in 1785, and set them in Salo.