fix: ensure BufferBuilder::truncate doesn't overset length#9288
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alamb merged 1 commit intoapache:mainfrom Jan 29, 2026
Merged
fix: ensure BufferBuilder::truncate doesn't overset length#9288alamb merged 1 commit intoapache:mainfrom
BufferBuilder::truncate doesn't overset length#9288alamb merged 1 commit intoapache:mainfrom
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Contributor
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I was going to suggest to
So agree, this makes the impl match the existing specification. 👍 |
Contributor
I think this is also consistent with |
Contributor
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Thanks again @Jefffrey and @jhorstmann |
Contributor
Author
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Thanks @yilin0518 for reporting this |
10 tasks
Contributor
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I think we should backport this to the 57 patch release I am preparing |
Contributor
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(I will make a PR to do so) |
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…9288) # Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. --> - Closes apache#9286 # Rationale for this change <!-- Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed. Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes. --> Miri reports undefined behaviour because `truncate` didn't check new length when setting the length for `BufferBuilder`, meaning when used in conjunction with `as_slice_mut` the pointer could potentially be dereferenced for memory beyond its allocation. # What changes are included in this PR? <!-- There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. --> Ensure we bound length in BufferBuilder so truncating to a larger length does not change the length. # Are these changes tested? <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> Added test. # Are there any user-facing changes? <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. If there are any breaking changes to public APIs, please call them out. --> No.
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Which issue does this PR close?
Rationale for this change
Miri reports undefined behaviour because
truncatedidn't check new length when setting the length forBufferBuilder, meaning when used in conjunction withas_slice_mutthe pointer could potentially be dereferenced for memory beyond its allocation.What changes are included in this PR?
Ensure we bound length in BufferBuilder so truncating to a larger length does not change the length.
Are these changes tested?
Added test.
Are there any user-facing changes?
No.