Bugfix: Check that read data has correct length #665
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dynamixels occasionally return a one byte (0x00) status when performing a sync read, this causes class GroupSyncRead.getData to crash with an index out of bounds exception
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Pull Request Overview
This PR fixes a bug where Dynamixel devices occasionally return truncated status packets (only one byte with 0x00) during sync read operations, causing index out of bounds exceptions in GroupSyncRead.getData. The fix adds length validation after extracting data from received packets to detect corrupted responses.
Key Changes
- Added data length validation in
readRxmethod to check if received data matches expected length - Added identical validation in
readTxRxmethod for consistency - Returns
COMM_RX_CORRUPTerror when data length mismatch is detected
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Summary of Changes
Hello @lupusorina, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request addresses a critical bug where the GroupSyncRead.getData method could crash due to an IndexError when Dynamixel devices occasionally return malformed data (e.g., a single 0x00 byte) instead of the expected data length. The changes introduce explicit data length validation in the packet handling functions to gracefully manage such corrupted responses.
Highlights
- Robust Data Validation: Implemented checks within readRx and readTxRx functions to validate that the length of received data from Dynamixel devices matches the expected length. This prevents IndexError exceptions caused by occasional one-byte (0x00) status returns during sync reads.
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Code Review
This pull request introduces a bugfix to prevent a potential index out of bounds exception when reading data from a Dynamixel device. The changes in readRx and readTxRx methods in protocol2_packet_handler.py add a crucial validation step to check if the length of the received data matches the expected length. If there's a mismatch, the communication result is marked as corrupt. This is a solid defensive programming practice that effectively addresses the problem. My review includes a suggestion to refactor the newly added, duplicated validation logic to improve long-term code maintainability.
| if len(data) != length: | ||
| result = COMM_RX_CORRUPT | ||
| return data, result, error |
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This data validation logic is also present in the readTxRx method (lines 626-628). To improve maintainability and avoid code duplication, consider extracting this logic into a private helper method. This would centralize the data extraction and validation, making the code easier to read and maintain in the future.
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Hi! Any update on this PR? Thanks |
2 participants
Dynamixels occasionally return a one byte (0x00) status when performing a sync read, this causes class GroupSyncRead.getData to crash with an index out of bounds exception.