Public lookup and unreflect cause a NPE

[John Rose]

On May 7, 2009, at 3:57 PM, John Rose wrote:

> On May 7, 2009, at 7:57 AM, Rémi Forax wrote:
>
>> I don't fully understand why this line is needed but
>> it can be easily solve by using == instead of equals (on Class ??)
>> if (lookupClass.equals(Access.class))  lookupClass = null;
>>
>> is replaced by:
>> if (lookupClass==Access.class)  lookupClass = null;
>
> Thanks for finding that bug.  (That was quick!)
>
> I'm trying to constrain the places where a null class can occur in  
> the access checking code, to reduce the chance of security bugs.  So  
> the NPE at that point is a feature, not a bug.  At some intermediate  
> point, the null class from PUBLIC_LOOKUP should be changed to the  
> special token Empty.class.
>
> At the JVM interface (and this should change) a null "caller class"  
> or "lookup class" means "all privileges".  The problem with that  
> convention is null is a very common error value produced by buggy  
> code, and we don't want somebody figuring out how to exploit the MH  
> package by introducing an unexpected null in a MH lookup.  I want an  
> NPE to happen before such an unplanned null is presented to the JVM.
>
> There is a currently empty "meth.patch" and "indy.patch" in the mlvm  
> repo. to collect these sorts of bug fixes.  I'll push a fix.

How time flies...  I'm working on loose ends post-JavaOne and will  
push a fix for this shortly.  (Regression tests included.)

-- John