If a NFSv4 mount is attempted  with string based options, and the
option string doesn't contain a clientaddr= option, the kernel will
currently oops. Check for this situation and return a proper error.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
 
                dprintk("MNTPATH: %s\n", *mntpath);
 
+               if (args.client_address == NULL)
+                       goto out_no_client_address;
+
                *ip_addr = args.client_address;
 
                break;
 out_no_address:
        dfprintk(MOUNT, "NFS4: mount program didn't pass remote address\n");
        return -EINVAL;
+
+out_no_client_address:
+       dfprintk(MOUNT, "NFS4: mount program didn't pass callback address\n");
+       return -EINVAL;
 }
 
 /*