Re: jdk.internal.reflect.ReflectionFactory and SecurityManager

Tue, 03 Jan 2017 23:16:39 -0800 

Hi David,

On 12/26/2016 10:16 PM, David Holmes wrote:

Hi Peter,
I know this is response to the problems with your other recent change, but this is an enhancement in my opinion, not a bug fix, and the time for enhancements is passed - though there is still a process to request them. I do not like to see last minutes changes like this where not enough due diligence may be done to identify all the ramifications.
Since the initialization cycle has now been broken by fix/simplification (JDK-8172048), there is no imminent need to pursue this one at this time, but...
The Class.getMethod() fixes seem to have overstepped the line in that regard as well, in my opinion. Anything that potentially changes initialization order is fragile and risky and requires additional testing.
...I was surprised that this actually happened at first. The initialization cycle was apparently introduced by my introduction of new class (java.lang.PublicMethods$Key) which in its <clinit> requests ReflectionFactory which does a permission check and all that is triggered from assertion in java.lang.invoke.VarHandle$AccessMode constructor which uses Class::getMethod to verify the assertion condition... 

Here's the stack trace, repeated here for clarity:

 Error occurred during initialization of VM
java.lang.ExceptionInInitializerError
at java.lang.PublicMethods$MethodList.filter(java.base@9-internal/PublicMethods.java:151) 
at java.lang.Class.getMethodsRecursive(java.base@9-internal/Class.java:3191)
at java.lang.Class.getMethod0(java.base@9-internal/Class.java:3175)
at java.lang.Class.getMethod(java.base@9-internal/Class.java:2036)
at java.lang.invoke.VarHandle$AccessMode.getReturnType(java.base@9-internal/VarHandle.java:1826) at java.lang.invoke.VarHandle$AccessMode.<init>(java.base@9-internal/VarHandle.java:1792) at java.lang.invoke.VarHandle$AccessMode.<clinit>(java.base@9-internal/VarHandle.java:1590) at java.lang.invoke.VarForm.linkFromStatic(java.base@9-internal/VarForm.java:127) 
at java.lang.invoke.VarForm.<init>(java.base@9-internal/VarForm.java:50)
at java.lang.invoke.VarHandleObjects$FieldInstanceReadOnly.<clinit>(java.base@9-internal/VarHandleObjects.java:84) at java.lang.invoke.VarHandles.makeFieldHandle(java.base@9-internal/VarHandles.java:38) at java.lang.invoke.MethodHandles$Lookup.getFieldVarHandleCommon(java.base@9-internal/MethodHandles.java:2241) at java.lang.invoke.MethodHandles$Lookup.getFieldVarHandle(java.base@9-internal/MethodHandles.java:2201) at java.lang.invoke.MethodHandles$Lookup.findVarHandle(java.base@9-internal/MethodHandles.java:1361) at java.util.concurrent.atomic.AtomicReference.<clinit>(java.base@9-internal/AtomicReference.java:57) 
at java.security.Policy.<clinit>(java.base@9-internal/Policy.java:111)
at java.security.AccessControlContext.getDebug(java.base@9-internal/AccessControlContext.java:110) at java.security.AccessControlContext.checkPermission(java.base@9-internal/AccessControlContext.java:398) at java.security.AccessController.checkPermission(java.base@9-internal/AccessController.java:894) at java.lang.SecurityManager.checkPermission(java.base@9-internal/SecurityManager.java:548) at java.lang.SecurityManager.checkPropertyAccess(java.base@9-internal/SecurityManager.java:1292) 
at java.lang.System.getProperty(java.base@9-internal/System.java:761)
at java.lang.ClassLoader.initSystemClassLoader(java.base@9-internal/ClassLoader.java:1902) 
at java.lang.System.initPhase3(java.base@9-internal/System.java:1979)
Caused by: java.lang.NullPointerException
at java.security.Policy.isSet(java.base@9-internal/Policy.java:126)
at java.security.AccessControlContext.getDebug(java.base@9-internal/AccessControlContext.java:110) at java.security.AccessController.checkPermission(java.base@9-internal/AccessController.java:871) at java.lang.SecurityManager.checkPermission(java.base@9-internal/SecurityManager.java:548) at jdk.internal.reflect.ReflectionFactory.getReflectionFactory(java.base@9-internal/ReflectionFactory.java:132) at jdk.internal.reflect.ReflectionFactory$GetReflectionFactoryAction.run(java.base@9-internal/ReflectionFactory.java:106) at jdk.internal.reflect.ReflectionFactory$GetReflectionFactoryAction.run(java.base@9-internal/ReflectionFactory.java:103) at java.security.AccessController.doPrivileged(java.base@9-internal/Native Method) at java.lang.PublicMethods$Key.<clinit>(java.base@9-internal/PublicMethods.java:90) at java.lang.PublicMethods$MethodList.filter(java.base@9-internal/PublicMethods.java:151) 
at java.lang.Class.getMethodsRecursive(java.base@9-internal/Class.java:3191)
at java.lang.Class.getMethod0(java.base@9-internal/Class.java:3175)
at java.lang.Class.getMethod(java.base@9-internal/Class.java:2036)
at java.lang.invoke.VarHandle$AccessMode.getReturnType(java.base@9-internal/VarHandle.java:1826) at java.lang.invoke.VarHandle$AccessMode.<init>(java.base@9-internal/VarHandle.java:1792) at java.lang.invoke.VarHandle$AccessMode.<clinit>(java.base@9-internal/VarHandle.java:1590) at java.lang.invoke.VarForm.linkFromStatic(java.base@9-internal/VarForm.java:127) 
at java.lang.invoke.VarForm.<init>(java.base@9-internal/VarForm.java:50)
at java.lang.invoke.VarHandleObjects$FieldInstanceReadOnly.<clinit>(java.base@9-internal/VarHandleObjects.java:84) at java.lang.invoke.VarHandles.makeFieldHandle(java.base@9-internal/VarHandles.java:38) at java.lang.invoke.MethodHandles$Lookup.getFieldVarHandleCommon(java.base@9-internal/MethodHandles.java:2241) at java.lang.invoke.MethodHandles$Lookup.getFieldVarHandle(java.base@9-internal/MethodHandles.java:2201) at java.lang.invoke.MethodHandles$Lookup.findVarHandle(java.base@9-internal/MethodHandles.java:1361) at java.util.concurrent.atomic.AtomicReference.<clinit>(java.base@9-internal/AtomicReference.java:57) 
at java.security.Policy.<clinit>(java.base@9-internal/Policy.java:111)
at java.security.AccessControlContext.getDebug(java.base@9-internal/AccessControlContext.java:110) at java.security.AccessControlContext.checkPermission(java.base@9-internal/AccessControlContext.java:398) at java.security.AccessController.checkPermission(java.base@9-internal/AccessController.java:894) at java.lang.SecurityManager.checkPermission(java.base@9-internal/SecurityManager.java:548) at java.lang.SecurityManager.checkPropertyAccess(java.base@9-internal/SecurityManager.java:1292) 
at java.lang.System.getProperty(java.base@9-internal/System.java:761)
at java.lang.ClassLoader.initSystemClassLoader(java.base@9-internal/ClassLoader.java:1902) 
at java.lang.System.initPhase3(java.base@9-internal/System.java:1979)
But even before my change, Class::getMethod needed access to ReflectionFactory instance. To remind: each reflective object (Method, Field, Constructor) is copied before handed out of a public method such as Class::getMethod. Copying is performed by ReflectionFactory. ReflectionFactory in java.lang.Class is obtained lazily: 

    // Fetches the factory for reflective objects
    private static ReflectionFactory getReflectionFactory() {
        if (reflectionFactory == null) {
            reflectionFactory =
                java.security.AccessController.doPrivileged
                    (new ReflectionFactory.GetReflectionFactoryAction());
        }
        return reflectionFactory;
    }
    private static ReflectionFactory reflectionFactory;
...so the only way for this to not cause the same problem is for Class.reflectionFactory field to be initialized before SecurityManager is set.
Was this pure luck and we were just waiting for a situation where this was not the case?
It is good that this danger is now past as java.security.Policy does not need AtomicReference any more. 

Regards, Peter



That said, I am an admirer of your work on OpenJDK! :)

Cheers,
David


On 27/12/2016 5:29 AM, Peter Levart wrote:

Hi,

There are 2 ReflectionFactory classes in JDK 9. The old one is
sun.reflect.ReflectionFactory which ended in jdk.unsupported module and
to which access is restricted with SecurityManager. There is also new
jdk.internal.reflect.ReflectionFactory which is used internally by JDK,
is exported to internal modules only but still uses SecurityManager to
restrict access to itself. I checked all usages and they all use
AccessControler.doPrivileged() for obtaining the instance of
jdk.internal.reflect.ReflectionFactory, which somehow defeats the
purpose of SecurityManager access checks in this API.

I think this could be simplified by removing the SecurityManager check
from jdk.internal.reflect.ReflectionFactory#getReflectionFactory static
method and change all usages to invoke this method directly without
doPrivileged(). There are already two sensitive internal APIs exposed
without SecurityManager checks: jdk.internal.misc.Unsafe#getUnsafe and
various jdk.internal.misc.SharedSecrets#getXxxAccess methods. So why
wouldn't internal ReflectionFactory be exposed the same way?

This would make obtaining the ReflectionFactory more robust and not
sensitive to bootstrap issues that surfaced recently after my push of a
fix for issues 8062389, 8029459, 8061950.

So, what do you think? Is this a worthwhile cleanup and simplification?

Regards, Peter

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