[SLING-6584] Race condition in ModelAdapterFactory

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Sling Models Impl 1.3.8
• Fix Version/s: Sling Models Impl 1.4.0
• Component/s: Extensions
• Assignee: Justin Edelson
• Reporter: Vlad Bailescu
• Created: 01/Mar/17 13:14
• Updated: 06/Dec/21 15:45
• Resolved: 01/Mar/17 14:59

Description

There is a possible race condition in https://github.com/apache/sling/blob/trunk/bundles/extensions/models/impl/src/main/java/org/apache/sling/models/impl/ModelAdapterFactory.java#L807-L815 when two threads are trying to inject the same field, resulting in model not being constructed.

try {
    if (!accessible) {
        field.setAccessible(true);
    }
    field.set(createdObject, result.getValue());
} catch (Exception e) {
    return new ModelClassException("Could not inject field due to reflection issues", e);
} finally {
    if (!accessible) {
        field.setAccessible(false);
    }
}

This is exposed by the unit test attached:

org.apache.sling.models.impl.ModelAdapterFactory - Could not adapt to model
org.apache.sling.models.factory.MissingElementsException: Could not inject all required fields into class org.apache.sling.models.testmodels.classes.WithOneConstructorModel
	at org.apache.sling.models.impl.ModelAdapterFactory.createObject(ModelAdapterFactory.java:593)
	at org.apache.sling.models.impl.ModelAdapterFactory.internalCreateModel(ModelAdapterFactory.java:335)
	at org.apache.sling.models.impl.ModelAdapterFactory.getAdapter(ModelAdapterFactory.java:211)
	at org.apache.sling.models.impl.ConstructorTest$1ModelCreator.call(ConstructorTest.java:153)
	at org.apache.sling.models.impl.ConstructorTest$1ModelCreator.call(ConstructorTest.java:149)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
	Suppressed: org.apache.sling.models.factory.MissingElementException: Could not inject private int org.apache.sling.models.testmodels.classes.WithOneConstructorModel.attribute
		at org.apache.sling.models.impl.ModelAdapterFactory.createObject(ModelAdapterFactory.java:598)
		... 8 more
	Caused by: org.apache.sling.models.factory.ModelClassException: Could not inject field due to reflection issues
		at org.apache.sling.models.impl.ModelAdapterFactory.setField(ModelAdapterFactory.java:812)
		at org.apache.sling.models.impl.ModelAdapterFactory.access$100(ModelAdapterFactory.java:112)
		at org.apache.sling.models.impl.ModelAdapterFactory$SetFieldCallback.inject(ModelAdapterFactory.java:378)
		at org.apache.sling.models.impl.ModelAdapterFactory.injectElement(ModelAdapterFactory.java:473)
		at org.apache.sling.models.impl.ModelAdapterFactory.createObject(ModelAdapterFactory.java:596)
		... 8 more
	Caused by: java.lang.IllegalAccessException: Class org.apache.sling.models.impl.ModelAdapterFactory can not access a member of class org.apache.sling.models.testmodels.classes.WithOneConstructorModel with modifiers "private"
		at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:101)
		at java.lang.reflect.AccessibleObject.slowCheckMemberAccess(AccessibleObject.java:295)
		at java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:287)
		at java.lang.reflect.Field.set(Field.java:755)
		at org.apache.sling.models.impl.ModelAdapterFactory.setField(ModelAdapterFactory.java:810)
		... 12 more

Issue Links

• is related to: SLING-10969 Remove synchronized & rest of accessible flag during injection