It may, ironically, help IS, if the Russians are attacking the Army of Conquest, who I think have been also fighting IS, as well as Assad. I think they are also supported by Turkey and the Saudis, and have been gaining a lot of territory. Thus, the Russians are trying to give Assad some breathing space. War by proxy, horrendous.
Another Machiavellian idea being floated, is that the Russians want to weaken non-IS groups, so that the West is forced to choose between Assad and IS. Who knows.