[release/dev17.14] Fix aligned buffer write #11862
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
![github-actions[bot]](https://avatars.githubusercontent.com/in/15368?s=60&v=4){kind=small}
This is a particularly subtle bug that requires a chunk (or remaining bit of a chunk) and the destination buffer being _exactly_ the same size. When this happens, the following sequence occurs: 1. `source.Length` and `destination.Length` are exactly aligned. This means that we do not enter the `if` on line 450, and `endOfChunkWritten` will be true. 2. We slice `destination` by `source.Length`. This leaves us with a `destination` that has 0 elements, and `IsEmpty` is true. 3. Because `endOfChunkWritten` is true, we enter the `if` on line 466. This increments us to the next chunk. 4. On line 472 (in the before diff), `destination.IsEmpty` is true, so we enter the `if`, and break out of the loop, never reseting `charIndex` to 0. 5. 4 happens again, this time on line 480 (in the before diff). Again, we do not reset `charIndex` to 0. To fix this, we want to unconditionally reset `charIndex` when we increment a chunk, not wait until after the destination has been checked for empty.
333fred
approved these changes
May 15, 2025
DustinCampbell
approved these changes
May 15, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Backport of #11861 to release/dev17.14
/cc @333fred
Customer Impact
Regression
Testing
Dedicated testing for the scenario was added.
Risk
Low. This fixes a small looping bug that only reproduces in particularly edge cases.