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runtime: deterministic fallback hashes across process boundary #66885

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prattmic opened this issue Apr 18, 2024 · 4 comments
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runtime: deterministic fallback hashes across process boundary #66885

prattmic opened this issue Apr 18, 2024 · 4 comments
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@prattmic
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done. release-blocker
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Go1.23

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@prattmic
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Map hashes use pre-process unique seeds to ensure that hashes differ across processes: aeskeysched for AES hash, and hashkey for fallback hash. Both are initialized in alginit.

https://go.dev/cl/516860 refactored the rand implementation in the runtime. Initialization of aeskeysched was changed to use bootstrapRand (available early), while hashkey was initialized with rand. rand's seed is not initialized until after alginit, so hashkey ends up with a deterministic value in every single process! Because hashkey is deterministic, so to are all (fallback) hashes.

cc @randall77 @rsc
@prattmic prattmic added NeedsFix The path to resolution is known, but the work has not been done. release-blocker labels Apr 18, 2024
@prattmic prattmic added this to the Go1.23 milestone Apr 18, 2024
@prattmic prattmic self-assigned this Apr 18, 2024
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Apr 18, 2024
@prattmic
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@gopherbot Please backport to 1.22. This regression makes map hashes deterministic across processes.

@gopherbot gopherbot mentioned this issue Apr 18, 2024
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Backport issue(s) opened: #66886 (for 1.22).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

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Change https://go.dev/cl/580136 mentions this issue: runtime: use bootstrapRand to initialize hashkey

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Change https://go.dev/cl/580018 mentions this issue: [release-branch.go1.22] runtime: use bootstrapRand to initialize hashkey

gopherbot pushed a commit that referenced this issue Apr 26, 2024
@prattmic @joedian
[release-branch.go1.22] runtime: use bootstrapRand to initialize hashkey
3f4af1f 
The seed for rand is not initialized until after alginit. Before
initialization, rand returns a deterministic sequence, making hashkey
deterministic across processes.

Switch to bootstrapRand, like other early rand calls, such as
initialization of aeskeysched.

For #66885.
Fixes #66886.

Change-Id: I5023a9161232b49fda2ebd1d5f9338bbdd17b1fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/580136
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
(cherry picked from commit 1a3682b)
Reviewed-on: https://go-review.googlesource.com/c/go/+/580018
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done. release-blocker
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