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8282144: RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes #3698

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8282144: RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes #3698

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@dtmhuang dtmhuang commented Jul 2, 2025 •
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Backport for RandomSupport issue. There is a loss of information when using convertSeedBytesToLongs() with a bad seed, causing a lot of the original bytes to be overwritten by 1s. The fix involves using a bitwise AND with the seed before distributing the seed bytes into the result.

Note there is an exact same issue/bugfix with convertSeedBytesToInts(), but I will backport that bugfix separately

Clean backport, ran GHA sanity checks and locally tested tier1, tier2. In tier2, there were 2 failures:
test/jdk/java/nio/channels/DatagramChannel/SendReceiveMaxSize.java
test/jdk/java/nio/channels/FileChannel/directio/DirectIOTest.java
However, these both failed before the backport as well.

The backport also includes the test for this issue T8282144.java, which passes.

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  • Change must not contain extraneous whitespace
  • Commit message must refer to an issue
  • JDK-8282144 needs maintainer approval

Issue

  • JDK-8282144: RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes (Bug - P4 - Approved)

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk17u-dev.git pull/3698/head

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https://git.openjdk.org/jdk17u-dev/pull/3698.diff

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bridgekeeper bot commented Jul 2, 2025

👋 Welcome back dtmhuang! 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.

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openjdk bot commented Jul 2, 2025 •
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@dtmhuang This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8282144: RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 12 new commits pushed to the master branch:

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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@openjdk openjdk bot changed the title Backport 5fab27e1b8fdf2ea27cb3b349bd339a4a6ec828b 8282144: RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes Jul 2, 2025
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openjdk bot commented Jul 2, 2025

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

@openjdk openjdk bot added backport Port of a pull request already in a different code base clean Identical backport; no merge resolution required labels Jul 2, 2025
@dtmhuang dtmhuang marked this pull request as ready for review July 2, 2025 20:41
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openjdk bot commented Jul 2, 2025

⚠️ @dtmhuang 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.

@openjdk openjdk bot added the rfr Pull request is ready for review label Jul 2, 2025
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dtmhuang commented Jul 2, 2025

/approval request
for backport of JDK-8282144 RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes

Motivation: Without this change, RandomSupport.convertSeedBytesToLongs() overrides many bits with 1s, resulting in a loss of information for some byte seeds.

Risk: Low. Ran GHA Sanity Checks, and tier 1 and tier 2 tests locally, as well as the testcase written specifically for this issue (T8282144.java). Patch is clean. Change has been present in tip since March, 2022.

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openjdk bot commented Jul 2, 2025

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8282144: The approval request has been created successfully.

@openjdk openjdk bot added approval Requires approval; will be removed when approval is received ready Pull request is ready to be integrated and removed approval Requires approval; will be removed when approval is received labels Jul 2, 2025
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dtmhuang commented Jul 8, 2025

/integrate

@openjdk openjdk bot added the sponsor Pull request is ready to be sponsored label Jul 8, 2025
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openjdk bot commented Jul 8, 2025

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Your change (at version 664cef1) is now ready to be sponsored by a Committer.

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/sponsor

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openjdk bot commented Jul 8, 2025

Going to push as commit 8b306de.
Since your change was applied there have been 12 commits pushed to the master branch:

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Jul 8, 2025
@openjdk openjdk bot closed this Jul 8, 2025
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Jul 8, 2025
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openjdk bot commented Jul 8, 2025

@phohensee @dtmhuang Pushed as commit 8b306de.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

@dtmhuang dtmhuang deleted the backport-8282144-RandomSupportLong branch July 8, 2025 15:59
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