Public lookup and unreflect cause a NPE

[John Rose]

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.

-- John