8282144: RandomSupport.convertSeedBytesToLongs sign extension overwrites previous bytes

[dtmhuang]

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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Progress

• 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 - Requested)

Reviewing

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$ git fetch https://git.openjdk.org/jdk17u-dev.git pull/3698/head:pull/3698
$ git checkout pull/3698

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

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$ git pr checkout 3698

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

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[bridgekeeper]

👋 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.

[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]

⚠️ @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.

[dtmhuang]

/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.

[mlbridge]

Webrevs

• 00: Full (664cef11)

[openjdk]

@dtmhuang
8282144: The approval request has been created successfully.