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List:       openjdk-hotspot-runtime-dev
Subject:    Integrated: 8286277: CDS VerifyError when calling clone() on object array
From:       Ioi Lam <iklam () openjdk ! java ! net>
Date:       2022-05-23 16:28:13
Message-ID: j6qnLhG2wSKI6LB5USKS_CH44kqnXXe6D4VjjKxOBPE=.7a8bd3e8-19d7-4408-81ec-ff124731e572 () github ! com
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On Mon, 16 May 2022 22:49:24 GMT, Ioi Lam <iklam@openjdk.org> wrote:

> **Problem:**
> 
> When verifying an invokevirtual bytecode that calls a protected method in a \
> superclass of the current class, the verifier requires that the object being \
> invoked must be a subtype of the current class. This prevents invocation of \
> protected methods in an unrelated class. For example, the following is disallowed \
> -- the type `InvokeCloneInvalid` cannot invoke `clone()` on a `String`: 
> 
> super public class InvokeCloneInvalid
> version 52:0
> {
> public static Method test:"(Ljava/lang/String;)V"
> stack 1 locals 1
> {
> aload_0;
> invokevirtual Method "java/lang/Object".clone:"()Ljava/lang/Object;";
> return;
> }
> }
> 
> 
> However, there's a special case where invoking `Object.clone()` is allowed on all \
> object arrays. Here's an example: 
> 
> super public class InvokeCloneValid
> version 52:0
> {
> public static Method test:"([Ljava/lang/Object;)V"
> stack 1 locals 1
> {
> aload_0;
> invokevirtual Method "java/lang/Object".clone:"()Ljava/lang/Object;";
> return;
> }
> 
> 
> Before this PR. the Verifier would first do the assignability check. When a failure \
> is encountered, the Verifier then checks for the special case and ignores the \
> failure accordingly. 
> In the above case, the assignability check will fail because the object being \
> invoked (an Object array) is not assignable to the current class (InvokeCloneValid) \
>  The problem is that CDS remembers all the assignability checks and tries to replay \
> them at runtime. Therefore, it will re-check the assignability of Object Array to \
> InvokeCloneValid, and throw a VerifyError as a result. 
> **Proposed Fix**
> 
> In `ClassVerifier::verify_invoke_instructions()`, check the special case first, \
> before doing the assignability check. This way, such invalid-but-ignored \
> assignability checks are no longer performed and thus won't be remembered by CDS. 
> **Testing**
> 
> Tiers 1 - 4, plus 3 new test cases.

This pull request has now been integrated.

Changeset: 646c8aae
Author:    Ioi Lam <iklam@openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/646c8aaeeccb494c72ff84c6e0f303f790be0ba9
                
Stats:     348 lines in 7 files changed: 339 ins; 0 del; 9 mod

8286277: CDS VerifyError when calling clone() on object array

Reviewed-by: dholmes, ccheung

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

PR: https://git.openjdk.java.net/jdk/pull/8737


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