In my town-home I have drywall wall in the attic (wall is between units).
I noticed that some tape came loose which made me think that the unfinished wall should get some protection with a primer. Painting in the attic woudl be difficult. However, I could spray with spray cans. Just wondering if there is such a prodcut: spray can primer?

 

Yep. Kilz original or Zinsser 123. But I would recommend you just take a couple 2x4 pieces of plywood up there so you have a "table" to set things on, a gallon of paint and a roller on a paint pole.

 

It's a wall in the attic and some of the tape has lifted?

Don't lose a night's worth of sleep, nothing is going to happen, your good!

 

Paint won't fix the lifting tape although it can stop the sound tape from coming loose. It's where the humidity has soaked into the joint compound and deteriorated it. I'd go with X's suggestion - lay a board down and roll a coat of paint or primer on. Spray cans don't go far and will tire your finger tip out before you finish. Rolled on paint will do a better job of sealing the drywall.

The tape is part of the fireproofing of the fire rock. Not a big deal if the rock was double laminated but many jurisdictions allow just one layer and then the tape becomes important.

 

I don't see a way to put up a 2x4 due to the joists, also my opening is limited. Certainly, rolling woudl be my preferred option.

So, if spray:
https://www.homedepot.com/p/KILZ-Ori...0044/100371323

Noticed it is oil based, assuming this has no impact on fire rating?

 

2x4s or a short section of plywood would lay across the joists so you have a place to stand/kneel and set your bucket of paint. Fire retardant paints are always latex based and while oil base paint is flammable I don't know if it would be a concern no more than you'd apply to the wall. IMO it would be cheaper/easier to roll a coat of latex paint or primer onto the wall. It's hard to get a coat thick enough [over a large area] to do much out of spray cans.