8360664: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object()

[savoptik]

The defect has been detected and confirmed in the function IterateOverHeapObjectClosure::do_object() located in the file src/hotspot/share/prims/jvmtiTagMap.cpp with static code analysis. This defect can potentially lead to a null pointer dereference.

The pointer oop o is passed to the constructor of the CallbackWrapper class, where it is dereferenced without a null check.

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Issues

• JDK-8360664: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object() (Bug - P4)
• JDK-8360670: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateThroughHeapObjectClosure::do_object() (Bug - P4)

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[mlbridge]

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• 01: Full - Incremental (e69c49c8)
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[savoptik]

/issue add 8360670

[openjdk]

@savoptik
Adding additional issue to issue list: 8360670: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateThroughHeapObjectClosure::do_object().

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[plummercj]

It's concerning that we don't have tests cases that uncover these bugs. Perhaps it's not actually possible for NULL to be passed when constructing CallbackWrapper.

[dholmes-ora]

I think this is a false positive from the static code analyzer. If we are iterating over the heap then the closure is only ever passed actual oops, so it can't be null.

At most I would add an assert, but generally my understanding is that the user of any closure has the responsibility of passing it valid input.

[sspitsyn]

At most I would add an assert, but generally my understanding is that the user of any closure has the responsibility of passing it valid input.

Adding asserts sounds like a good suggestion.

[sspitsyn]

I'm a little bit confused why we have twp bugs for this issue.
The bug JDK-8360670 seems to be a dup of:
JDK-8360664: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object()
Should it be closed as a dup?

[savoptik]

At most I would add an assert, but generally my understanding is that the user of any closure has the responsibility of passing it valid input.

Adding asserts sounds like a good suggestion.

It seems to me that this won’t be a big problem in this form. I’ve just moved the existing check higher up, where it will prevent dereferencing a null pointer.

However, if you confirm that this is not acceptable, I will replace the check with assert.

[plummercj]

At most I would add an assert, but generally my understanding is that the user of any closure has the responsibility of passing it valid input.

Adding asserts sounds like a good suggestion.

It seems to me that this won’t be a big problem in this form. I’ve just moved the existing check higher up, where it will prevent dereferencing a null pointer.

However, if you confirm that this is not acceptable, I will replace the check with assert.

I think it is a matter of having the code accurately document the input requirements. Checking for null and returning makes it look like passing null is ok and might happen. That's not the case though. It should never happen and adding an assert properly documents this.