I just checked. You're right, my description was incomplete.

You can get that error from a large variety of interrupts and exceptions. The case that I described is when a normally working program has an illegal instruction because what was supposed to be code was overwritten (eg by a buffer overrun). But you can get the same error if you, for instance, attempt to access a memory address that isn't mapped.

In the event of a buffer overrun that overruns just slightly, it is far more likely that you would overwrite code than that you would access memory outside of what is mapped. But missing the buffer due to a programming bug could easily be accessing wild memory addresses, giving the same error through a wildly different cause.