assert macro to check null

I have developed a driver which has become unstable. Now when I debug,I find that it is crashing at http://lxr.free-electrons.com/source/kernel/cred.c?v=3.8#L431 get_cred(new); where null is struct cred *new. I think this new might be NULL. Now I plan to add an assert in our macro that deals with creds, like for asserting passed object isn't NULL. Any suggestions as to how I can do that? Regards, Saket Sinha