RFR: 6726901: JDWP: ReferenceType.GetValues crashes jvm in case non-static fields are passed [v2]

[Chris Plummer]

On Thu, 21 Nov 2024 21:26:01 GMT, Adam Bruce <duke at openjdk.org> wrote:

>> This PR fixes a long-standing bug in JDWP where the access flags of a field are not checked before attempting to read it's value. 
>> 
>> Prior to this change, attempting to read a non-static field would cause a JVM crash, this change corrects that behaviour by returning `INVALID_FIELDID` instead.
>> 
>> This is my first PR to OpenJDK, so please let me know if I've made any mistakes in the process.
>> 
>> Cheers,
>> Adam
>
> Adam Bruce has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Move static check to sharedGetFieldValues, add JDWP tests

src/jdk.jdwp.agent/share/native/libjdwp/util.c line 516:

> 514: 
> 515:     if (!isStatic) {
> 516:         clazz = JNI_FUNC_PTR(env,GetObjectClass)(env, object);

You need to free the jobject before exiting this function. Note you only do this if clazz is allocated here. The assignment to clazz above is from a jobject that the debug agent is managing (as part of mapping JDWP ObjectIDs to jobjects), so it should not be freed for the static case.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/22280#discussion_r1857397453