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

[ExE Boss]

On Wed, 20 Apr 2022 07:27:01 GMT, David Holmes <dholmes 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.
>
> I admit I'm still not completely clear on the exact situation here in terms of what code is invoking what method with what receiver. If the bytecode is malformed then that should have been detected before now - as long as verification has not been disabled.

@dholmes-ora
From my understanding, the bytecode is correct, but the third‑party serialisation library ends up incorrectly deserialising the `LongMapSupportArrayList` instance as an `ArrayList`, and then uses `Unsafe.setObject` to store it in the `longValues` field, which is typed as `LongMapSupportArrayList`.

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Then, when the `getValuesMap()` method calls `this.longValues.toMap()`, the JVM assumes that since `longValues` is typed as `LongMapSupportArrayList`, the `LongMapSupportArrayList.toMap:()Ljava/util/Map;` method will always exist, but since the `longValues` field now contains a `java.util.ArrayList` (which doesn’t have the `toMap()` method), the `vtable` index is invalid, which leads to a VM crash.

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