These men were mostly of average height. Lenin was born in 1870, that age cohort's the average height was 5'5". Stalin was born in 1878, when it had risen slightly to be somewhat less than 5'6". Khruschev in 1894, when the average height was approaching 5'7", and thus is the only one notably shorter than his cohort. Khruschev's parents were also notably poor, meaning poor nutrition might have affected his growth. WW1 (when Kruschev was 20-24) also saw a sharp decrease in standards of living that couldn't have helped.

As far as I'm aware, the Soviet Union had no official position towards short people. The Soviet Union was pro-proletariat, who were, in general, the poorer members of Russia. Poor people in Russia, especially in times of dearth, sometimes suffered famine and never ate as well as those with more money. (This is nearly tautological: people with less money to buy food could buy less food.) Early childhood nutritional deficiencies have a variety of effects, but one of them is that, even later in life, you don't grow as tall. So the Soviet focus on preventing the upper classes and bourgeoisie from entering government, and their encouragement of peasants and factory workers, meant they were drawing from the (on average) shorter classes of the former Russian Empire.

But as far as I know, there's been no research into the subject specifically.

More figures, for the record. Note that these are common estimates drawn from a variety of web sources:

Putin stands at roughly 5' 6 1/2;" Dmitry Medvedev-- 5' 4;" Mikael Gorbachev-- 5' 9;" Leonid Brezhnev-- 5' 8."

Boris Yeltsin seems to be the major outlier at 6'2".