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JNI global references leak when native method registration fails

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
66/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
c, java
Domain
backend

Research direction

Start in native/dispatch.c at Java_com_sun_jna_Native_registerMethod, especially the cleanup path reached after ffi_prep_cif, ffi_closure_alloc, or ffi_prep_closure_loc fails. Trace ownership of closure_method, from_native, to_native, closure_arg_types, encoding, and the FFI closure, then verify failed registrations release them while successful registrations still transfer cleanup to Native_unregister.

Written by the indexing model from the issue text.

Description

Summary

Java_com_sun_jna_Native_registerMethod creates persistent JNI references before several fallible FFI initialization steps.

Affected code:
https://github.com/java-native-access/jna/blob/d036ad9781adad4b66693e8fa7098e4ac665e0a3/native/dispatch.c#L3553-L3587

If ffi_prep_cif, ffi_closure_alloc, or ffi_prep_closure_loc fails, execution jumps to cleanup. That path frees data without calling DeleteGlobalRef for data->closure_method.

Because registration did not complete, Native_unregister cannot release this reference later.

Impact

Each failed registration permanently retains the reflected Java Method and potentially its class-loader object graph until JVM shutdown. Repeated failures may cause persistent memory growth.

The same cleanup path also omits some related resources, including weak global references, closure_arg_types, encoding, and an allocated FFI closure.

Suggested fix

Before freeing data on failure:

  • Delete closure_method with DeleteGlobalRef.
  • Delete any from_native and to_native weak global references.
  • Free all allocated arrays, encoding data, and FFI closure memory.

Successful registrations should continue to transfer ownership to Native_unregister.

Dominant language
Java
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