The home side had lost four successive games 1-0, and looked set for the same fate until Gall cleverly found space to drill a low right-foot shot into the corner from 15 yards on 71 minutes.
Cheltenham had gone ahead after 32 minutes when Justin Richards tapped in at the far post after Marley Watkins carved open the Darlington defence.
Earlier Darlington had enjoyed the better of it, Gall flashing a drive wide of the near post after the impressive Nathan Porritt picked him out.
After 52 minutes Cheltenham substitute Josh Low could have made the game safe but after racing clear from the half-way line he fired tamely at keeper David Knight.
Once Darlington had equalised they went all out for a winner and almost got it deep in stoppage time. Jordan Cook crossed low from the right and David Dowson almost tucked the ball in but could not quite connect cleanly.