"Lastly, the baseband processor is usually the master processor, whereas the application processor (which runs the mobile operating system) is the slave."
Can maybe somebody explain what this means exactly? Could the baseband processor/OS be used as an attack vector to exploit the main mobile OS? Could the OS protect itself from this?
The baseband processor may have unrestricted access to the entire address space of the device or to address space which the application processor (and the operating system it's running) implicitly trusts.
AFAIK, access to the baseband and vice versa is through a network inside the phone. Physically, these two computers are separated, and communicate only through a well-defined network interface. No poking in other computer's memory.
Most modern phones don't really have a physically separate baseband processor and application processor, they run a real-time microvisor (usually an L4 based system, and frequently OKL4 - see http://wiki.ok-labs.com/#OKL4Microvisor4.0). The microvisor runs multiple virtual 'cells' (which are ARM operating systems that think they are running as supervisor), and ensures that the hard realtime requirements of the radio driver are met even if the kernel in the application cell is stuck in a loop.
Because the application processor is actually running in a virtual cell and not on bare metal, it doesn't have full access to the hardware and can't interfere with the radio cell - but the radio cell might still have access to everything.
Can maybe somebody explain what this means exactly? Could the baseband processor/OS be used as an attack vector to exploit the main mobile OS? Could the OS protect itself from this?