RFR: 8258077: Using -Xcheck:jni can lead to a double-free after JDK-8193234

[David Holmes]

On Thu, 10 Dec 2020 17:55:30 GMT, Mauro Lacy <github.com+11656534+maurolacy at openjdk.org> wrote:

>> Hello,
>> 
>> I'm a contributor of the [jni-rs](https://github.com/jni-rs/jni-rs/) project. Rust bindings to the JNI. 
>> 
>> When running tests against OpenJDK with the flag "-Xcheck:jni" enabled, we detected the following: the behaviour of the `JNI_COMMIT` mode of `ReleasePrimitiveArrayCritical` seems to be inconsistent, when running with `-Xcheck:jni` enabled, vs. without `-Xcheck:jni`.
>> 
>> If using "-Xcheck:jni", we're hitting a double free calling `ReleasePrimitiveArrayCritical` with `JNI_COMMIT`, when we attempt to release the buffer at the end. It is our understanding that the behaviour of `ReleasePrimitiveArrayCritical` must be consistent, independently of whether the check JNI mode is enabled or not.
>> 
>> You can check [https://github.com/jni-rs/jni-rs/issues/283](https://github.com/jni-rs/jni-rs/issues/283) for details / comments on this.
>> 
>> We've tracked down the issue to this February 2019 commit: [openjdk commit 3e904a4](https://github.com/openjdk/jdk/commit/3e904a4801b2bf2e988ba096e5cb64a17fd5fce7). The related discussion is here: [openjdk bug JDK-8193234](https://bugs.openjdk.java.net/browse/JDK-8193234).
>> 
>> As there are no associated tests or functionality in the OpenJDK code base, I've simply reverted the commit. Just in case, I've also built and tested the JDK, without issues.
>> 
>> Not sure what tests are the ones mentioned in the discussions that led to the introduction of this behaviour. It is our understanding that tests of `JNI_COMMIT` functionality must still make a call to `ReleasePrimitiveArrayCritical` with a proper mode (`0` or `JNI_ABORT`) at the end, to release the buffer. And this, independently of `-Xcheck:jni` being enabled or not.
>> 
>> If there are any issues related to this that we're not aware of, please let us know.
>> 
>> This reverts commit 3e904a4801b2bf2e988ba096e5cb64a17fd5fce7.
>
> issue 8193234: When using -Xcheck:jni an internally allocated buffer can leak (original issue).

I've filed: https://bugs.openjdk.java.net/browse/JDK-8258077

Cheers,
David

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PR: https://git.openjdk.java.net/jdk/pull/1697