Never trust external content for FString#9145
Merged
headius merged 1 commit intojruby:masterfrom Dec 18, 2025
Merged
Conversation
When creating an FString for the first time, we should never trust that the incoming byte[] or ByteList are now ours to own. The caller might still have a reference to them that they continue to modify, resulting in a zombie FString that can't be found or that has incorrect contents. This came up while trying to implement the "fake string" optimization for uncached headers in puma/puma#3838. Holding a reference to a RubyString and its ByteList that could be updated in-place and then used to caches new headers led to those cached FStrings being modified directly.
headius
added a commit
that referenced
this pull request
Dec 18, 2025
Member
Author
|
Pushed a test after merge in 1cb0236 |
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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
When creating an FString for the first time, we should never trust that the incoming byte[] or ByteList are now ours to own. The caller might still have a reference to them that they continue to modify, resulting in a zombie FString that can't be found or that has incorrect contents.
This came up while trying to implement the "fake string" optimization for uncached headers in puma/puma#3838. Holding a reference to a RubyString and its ByteList that could be updated in-place and then used to caches new headers led to those cached FStrings being modified directly.