This has been a problematic product from what I've read if it was installed sometime in the '80s to 1996. FWIW, you may be OK but it's worth taking a few minutes to see if there's more to your siding than what you know.
I found a great site for you. It's Home Repair, and it has a link for Masonite Corporation that has a download capability to tell you how to Install AND Maintain Masonite Siding. On the aforementioned WEB page, go to the Masonite Siding link, click it, and go from there. You'll scroll down to 'click' which product you have, then you'll be asked to download the information. You'll need Adobe Acrobat Reader if you don't have it. (You'll see it mentioned once you go to the Masonite Siding page.) If you need more help, perhaps tell us the specific problem (about the repair you want to do) and we'll see who responds.