On Mon, 11 Aug 2025 11:33:19 GMT, Per Minborg <pminb...@openjdk.org> wrote:
> ### Description
> This PR proposes to update the `ClassLoader` implementation to properly guard
> access to the provided `ByteBuffer` when defining a class using
> `defineClass(String, ByteBuffer, ...)`. Specifically, calls to
> `SharedSecrets.getJavaNioAccess().acquireSession(ByteBuffer)` and
> `releaseSession(ByteBuffer)` have been introduced to ensure safe and
> consistent buffer access throughout the native class definition process, even
> in the case of a `ByteBuffer` is backed by a `MemorySegment`.
>
> ### Impact
> This modification is internal to the `ClassLoader` implementation and does
> not affect the public API.
> Improves the robustness and security of class loading from buffers.
>
> ### Testing
> Tier 1, 2, and 3 JDK tests pass on multiple platforms.
test/jdk/java/lang/ClassLoader/defineClass/GuardByteBuffer.java line 58:
> 56: };
> 57: final List<Thread> threads = new ArrayList<>();
> 58: for (int i = 0; i < Runtime.getRuntime().availableProcessors();
> i++) {
This means all cores spinning for 20s - we'll have to see if it causes any side
effects and slow down of other tests that happen to run at the same time in
other agent VMs (make run-test uses concurrency by default).
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PR Review Comment: https://git.openjdk.org/jdk/pull/26724#discussion_r2267040749
