Bugfix for incorrect parameters seen in br_table and end hooks#50
Merged
Conversation
The br_tables vector can be modified concurrently. A reader/writer lock correctly protects this, however, the lock is dropped briefly between adding a new item and calculating the new item's index. This therefore allows a race condition in which another writer modifies the vector before the index is calculated. This fix holds the lock whilst the index is calculated.
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
2 participants
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
A concurrency bug can corrupt the output in large wasm files containing many
br_tableinstructions whenendorbr_tablehooks are enabled. This leads to incorrect information being passed to the hook forbr_tableinstructions, orendinstructions if the output happens to be corrupted. In a large example benchmark with more than 200 functions and more than 50br_tableinstructions, this meant that the output was always wrong.The bug is caused because the
br_tablesvector can be modified concurrently. A reader/writer lock correctly protects this, however, the lock is dropped briefly between adding a new item and calculating the new item's index. This therefore allows a race condition in which another writer modifies the vector before the index is calculated. This fix holds the lock whilst the index is calculated.