argv and envp are pointers to u32's in userspace, so don't
try to put_user() a NULL to them.
Aparently gcc-4.2.x now warns about this, and since we use
-Werror for arch/sparc64 code, this breaks the build.
Signed-off-by: David S. Miller <davem@davemloft.net>
                        get_user(c,p++);
                } while (c);
        }
-       put_user(NULL,argv);
+       put_user(0,argv);
        current->mm->arg_end = current->mm->env_start = (unsigned long) p;
        while (envc-->0) {
                char c;
                        get_user(c,p++);
                } while (c);
        }
-       put_user(NULL,envp);
+       put_user(0,envp);
        current->mm->env_end = (unsigned long) p;
        return sp;
 }