On Tue, 16 Dec 2025 20:21:59 GMT, Chen Liang <[email protected]> wrote:
>> ASAN correctly detected a use-after-free in this test.
>>
>> The issue is that an async `ScopedAccessError` is thrown while executing
>> java code as part of a JVMTI callback. This exception is meant to unwind out
>> of a scoped memory access, to prevent access to memory that has already been
>> freed. But, currently the native agent code is printing and clearing the
>> exception, which doesn't prevent the memory access from occurring, leading
>> to a use-after-free.
>>
>> Ideally, the agent should propagate the exception to the place in the Java
>> code where the JVMTI event happens, but it is not possible to exit the
>> callback with a pending exception, and AFAICT there is no JVMTI API for
>> propagating async exceptions that are thrown during a JVMTI callback. So,
>> the only sane thing the test can do is exit the process, which is what I've
>> implemented here.
>>
>> This fixes the test, but it leaves the larger question of how JVMTI agents
>> should deal with async exceptions unresolved.
>
> test/jdk/java/foreign/sharedclosejvmti/libSharedCloseAgent.cpp line 109:
>
>> 107: jni_env->ExceptionDescribe();
>> 108: if (jni_env->IsInstanceOf(ex, EXCEPTION_CLS)) {
>> 109: exit(0); // success
>
> Just curious, does this just terminate the agent? If this terminates the JVM,
> how is the checked string printed:
>
> output.stderrShouldContain("Exception in thread "Trigger"
> jdk.internal.misc.ScopedMemoryAccess$ScopedAccessError: Invalid memory
> access");
It terminates the VM. That string is printed by `ExceptionDescribe()`
> test/jdk/java/foreign/sharedclosejvmti/libSharedCloseAgent.cpp line 115:
>
>> 113: }
>> 114:
>> 115: jvmti_env->Deallocate((unsigned char*) method_name);
>
> We can move the 2 Deallocate to right above CallStaticVoidMethod.
Cleaned this code up a bit. We just need one call to `Deallocate` for each
string.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/28853#discussion_r2624641725
PR Review Comment: https://git.openjdk.org/jdk/pull/28853#discussion_r2624662418
