8391041: RISC-V: Fix out-of-bounds read in string_indexof_char intrinsic

[RealFYang]

Hi all,

This pull request contains a backport of commit 660dd42d from the openjdk/jdk repository.

The commit being backported was authored by Chuanqi Zang on 26 Aug 2026 and was reviewed by Dingli Zhang and Fei Yang.

Thanks!

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Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8391041 needs maintainer approval

Issue

• JDK-8391041: RISC-V: Fix out-of-bounds read in string_indexof_char intrinsic (Bug - P4 - Requested)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/763/head:pull/763
$ git checkout pull/763

Update a local copy of the PR:
$ git checkout pull/763
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/763/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 763

View PR using the GUI difftool:
$ git pr show -t 763

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/763.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back fyang! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

⚠️ @RealFYang This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[RealFYang]

/approval request jdk25u-dev repo bears the same issue. We should backport in order to fix the out-of-bound memory access issue in the string_indexof_char intrinsic. This is a RISC-V CPU specific change. Verified with tier1-3 tests on linux-riscv64 platform.

[openjdk]

@RealFYang
8391041: The approval request has been created successfully.

[mlbridge]

Webrevs

• 00: Full (22246fd5)