On 6/23/14, 9:36 PM, Mandy Chung wrote:
Coleen,
On 6/23/2014 4:45 PM, Coleen Phillimore wrote:
Please review a change to the JDK code for adding classLoader field
to the instances of java/lang/Class. This change restricts
reflection from changing access to the classLoader field. In the
spec, AccessibleObject.setAccessible() may throw SecurityException if
the accessibility of an object may not be changed:
http://docs.oracle.com/javase/7/docs/api/java/lang/reflect/AccessibleObject.html#setAccessible(boolean)
Only AccessibleObject.java has changes from the previous version of
this change.
This change looks reasonable. As a side note: Joel mentions about
the mechanism to hide class members from reflection. I discussed
with Joel offline before he went on parental leave and suggest that we
should revisit the two mechanisms that both effectively disallow
access to private members in the future.
Thanks, Mandy. Yes, let me know what you come up with and we can
improve this. Thank you for the help fixing this bug.
Coleen
Mandy
open webrev at http://cr.openjdk.java.net/~coleenp/6642881_jdk_4/
bug link https://bugs.openjdk.java.net/browse/JDK-6642881
Thanks,
Coleen
On 6/19/14, 11:01 PM, David Holmes wrote:
On 20/06/2014 6:53 AM, Joel Borggrén-Franck wrote:
Hi Mandy,
On 19 jun 2014, at 22:34, Mandy Chung <mandy.ch...@oracle.com> wrote:
On 6/19/14 12:34 PM, Joel Borggrén-Franck wrote:
Hi,
On 19 jun 2014, at 20:46, Coleen Phillimore
<coleen.phillim...@oracle.com> wrote:
On 6/17/14, 12:38 AM, Joel Borggrén-Franck wrote:
Have you considered hiding the Class.classLoader field from
reflection? I’m not sure it is necessary but I’m not to keen on
the idea of people poking at this field with Unsafe (which
should go away in 9 but …).
I don't know how to hide the field from reflection. It's a
private final field so you need to get priviledges to make it
setAccessible. If you mean injecting it on the JVM side, the
reason for this change is so that the JIT compilers can inline
this call and not have to call into the JVM to get the class
loader.
There is sun.reflect.Reflection.registerFieldsToFilter() that
hides a field from being found using reflection. It might very
well be the case that private and final is enough, I haven’t
thought this through 100%. On the other hand, is there a reason
to give users access through the field instead of having to use
Class.getClassLoader()?
There are many getter methods that returns a private final field.
I'm not sure if hiding the field is necessary nor a good precedence
to set. Accessing a private field requires "accessDeclaredMember"
permission although it's a different security check (vs
"getClassLoader"
permission). Arguably before this new classLoader field, one could
call Class.getClassLoader0() via reflection to get a hold of class
loader.
Perhaps you are concerned that the "accessDeclaredMember" permission
is too coarse-grained? I think the security team is looking into
the improvement in that regards.
I think I’m a bit worried about two things, first as you wrote,
“accessDeclaredMember” isn’t the same as “getClassLoader”, but
since you could get the class loader through getClassLoader0() that
shouldn’t be a new issue.
The second thing is that IIRC there are ways to set a final field
after initialization. I’m not sure we need to care about that
either if you need Unsafe to do it.
Normal reflection can set a final field if you can successfully call
setAccessible(true) on the Field object.
David
-----
cheers
/Joel