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fn AlignedVec::resize: Validate safety requirements, specifically overflow #1357

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HeroicKatora
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@HeroicKatora HeroicKatora commented Sep 10, 2024

This is a necessary check for soundness, as demonstrated by the test which can SIGSEGV without the check. Before the check, an overflow in the underlying buffer calculation can create incoherent state where the vector believes in an impossibly large buffer of the item type which is not actually backed by a correctly sized buffer of chunks.

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@kkysen kkysen self-requested a review September 10, 2024 16:37
@kkysen kkysen self-assigned this Sep 10, 2024
This is a necessary check for soundness, as demonstrated by the test
which can SIGSEGV without the check. Before the check, an overflow in
the underlying buffer calculation can create incoherent state where the
vector believes in an impossibly large buffer of the item type which is
not actually backed by a correctly sized buffer of chunks.
@HeroicKatora HeroicKatora force-pushed the issue-1356-aligned-vec-overflow branch from 3b72c9a to 556beac Compare September 10, 2024 20:41
@kkysen kkysen changed the title Validate AlignedVec::resize safety requirements fn AlignedVec::resize: Validate safety requirements, specifically overflow Sep 17, 2024
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Thanks for finding this bug and the PR!

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LGTM now except for that one little comment. Appreciate the NOTEs, too.

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LGTM now. @HeroicKatora, I'll merge it now assuming you're all done with it. Thanks again!

@kkysen kkysen merged commit b417059 into memorysafety:main Sep 23, 2024
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@HeroicKatora HeroicKatora deleted the issue-1356-aligned-vec-overflow branch September 23, 2024 10:09
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Overflows can unsoundly taint length state in AlignedVec
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