You don't need to mask the bloom and glare pass - when you are using an Add mode, whether Linear or not, black "adds nothing" automatically, ie has no effect, ie is like it is masked without ever having to mask it.
(EDIT and similarly "faint" bloom and glare "adds just a little", ie also looks like there is a mask of some grey there... and "really bright" bloom and glare will add so much it pretty much wipes out what was underneath it, just like a mask of "full white" would.... the Add mode is the key, as you are adding a light source which works in an add mode, not adding a sticker or other overlay that would require a mask e.g. like a tree cutout would need a mask as it is not lighting but an object, so needs to be layered in normal mode with a mask )