Atletico, one point closer to Barcelona in second spot, could only manage a dour 0-0 draw at home to Villarreal.
Barcelona, who won 2-1 at Las Palmas on Saturday, have 63 points to Atletico's 55 and 54 for Real before the Madrid derby at the Bernabeu next Saturday.
Spanish media headlines sounded the death knell for Real's title hopes, saying they had kissed the La Liga crown goodbye.
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Ronaldo put Real ahead when he rose unmarked but in an offside position to head a Toni Kroos free kick over Carlos Kameni in the 33rd minute for his 22nd league goal this season.
He was denied a second goal three minutes later as Kameni dived to his left to save Ronaldo's spot kick after the Portuguese forward was brought down by Weligton.
Malaga scored a deserved equaliser in the 66th minute when central defender Raul Albentosa, unmarked in the middle of the box, volleyed home a cross from the left.
GREAT TEAM
"Malaga are a great team, they made it tactically difficult. Today we failed but we won't surrender, we'll fight to the end," Real left back Marcelo said. "The draw tastes like a defeat."
The home side would not have been flattered with a victory as Real were indebted to goalkeeper Keylor Navas who twice denied Charles, Juanpi and Duje Cop.
Kameni also made saves from Sergio Ramos and Jese but Malaga were the more cohesive team and Real missed the thrust of a centre forward with Karim Benzema absent through injury.
The only consolation for visiting coach Zinedine Zidane was that the draw at least extended his unbeaten run in his new job to eight matches in both La Liga and the Champions League.
"We did a good job, you can see teams find it hard to score against us," said Albentosa, who is on loan at Malaga from English Championship (second-tier) side Derby County.
"Our objective is still survival (in the top flight), fight in all our matches and get all the points we can."
Malaga are 12th on 31 points, 10 above the relegation zone but have been caught by Valencia after Gary Neville's team won 2-1 at Granada for a second successive league win.
"We've had a fantastic week, three matches three wins," said Valencia midfielder Daniel Parejo, who opened the scoring, as he included Thursday's 6-0 Europa League rout of Rapid Vienna.
(Writing by Rex Gowar; editing by Ian Chadband and Ken Ferris)
