Lonewolf,
The Iraqi's have been allowing Russian bombers and cruise missiles to overfly from Iranian airspace since 2015. Tu-22M3 Backfires were regularly flown over Iran/Iraq to attack targets in Syria. See following from 2015 showing Iranian fighters escorting Tu-95MS Bear H before they launched their cruise missiles over Iranian airspace into Syria.
https://theaviationist.com/2015/11/2...rt-ruaf-tu-95/
"The Russians did notify the coalition as per the memorandum of understanding for safety of flight," said U.S. military spokesman Col. Chris Graver. "They informed us they were coming through and we ensured safety of flight as those bombers passed through the area and toward their target and then when they passed out again."
U.S. cleared Iraqi airspace so Russia could bomb non-ISIS targets in Syria | Washington Examiner