RFR: 8284877: Check type compatibility before looking up method from receiver's vtable

[David Holmes]

On Thu, 14 Apr 2022 10:40:21 GMT, Yi Yang <yyang at openjdk.org> wrote:

> Hi, can I have a review for this enhancement? This patch adds type compatibility check before method lookup for robustness. In some internal cases, serialization framework may improperly generate an object of wrong type, which leads JVM randomly crashes during method resolution.
> 
> For example:
> 
> invokevirtual selected method: receiver-class:java.util.ArrayList, resolved-class:com.taobao.forest.domain.util.LongMapSupportArrayList, resolved_method:com.taobao.forest.domain.util.LongMapSupportArrayList.toMap()Ljava/util/Map;, selected_method:0x458, vtable_index:56#
> 
> The real type of receiver is ArrayList, while the resolved method is LongMapSupportArrayList.toMap. VM attempts to select method as if looking up from receiver's vtable via vtable index of resolved method(i.e. attempts to lookup `toMap()` from 
>  ArrayList), an invalid method or incorrect method would be selected, thus causing some strange crashes.
> 
> I think it's reasonable to add a type compatibility check before method lookup. If such an incompatible call is found, JVM could throw an exception instead.

If Unsafe is being used to circumvent the type system, then we should not be adding additional checks in the VM to catch that later. If you use Unsafe directly and you do it wrong then you can crash the VM - that is not a VM problem to fix.

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PR: https://git.openjdk.java.net/jdk/pull/8241