So the Russian government, electing to support the Assad government in this theatre of the current regional war, is deploying fighter and strike aircraft, as well as surface-air-missile systems to Syria.
ISIS has no air force so the Russian air defence toys aren't meant for them. Israel, Turkey, maybe Iran, and the US-led coalition allies (including Canada) all do and all three fly or flown missions over Syria. Not to mention the Syrian's loyal to Assad themselves
Russia might well see Syria as an opportunity to both support its client state, and more importantly, hard leverage against the US and allies presently behind Ukraine inspired sanctions, to cut a deal over cooperation against ISIS, say for sanction relief or something to do with Ukraine. Or risk an incident.