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Fix deadlock when handling bad calls to batch_funding.._generated #2841

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TheBlueMatt
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When handling calls to batch_funding_transaction_generated which were missing outputs for one of the batch channels, we'd previously deadlock when trying to clean up the now-closed channels. This fixes that and adds a new test case for it.

Found by the full_stack_target fuzzer.

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coderabbitai bot commented Jan 22, 2024

Walkthrough

The update includes a crucial fix to resource management by explicitly releasing funding_batch_states before entering a loop to process shutdown_results. This prevents potential deadlocks, enhancing stability. Additionally, the test suite has been expanded with new tests to ensure the robustness of force-close handling and batch funding failure scenarios, safeguarding against previously identified deadlock issues during channel shutdown procedures.

Changes

File Path Change Summary
lightning/src/ln/channelmanager.rs Introduced memory resource release before processing shutdown results and added logic to handle channel closure.
lightning/src/ln/shutdown_tests.rs Added tests for force-close handling and batch funding failure to address deadlock situations.

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To code we hop, with care we leap,
Patching the holes where bugs might creep.
With tests we bound, and deadlocks flee,
In our digital burrow, we code free. 🌟🐾

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Review Status

Actionable comments generated: 1

Configuration used: CodeRabbit UI

Commits Files that changed from the base of the PR and between 6b0ba8c and ec79a63.
Files selected for processing (2)
  • lightning/src/ln/channelmanager.rs (1 hunks)
  • lightning/src/ln/shutdown_tests.rs (3 hunks)
Additional comments: 2
lightning/src/ln/channelmanager.rs (2)
  • 3987-3987: Explicitly dropping funding_batch_states using mem::drop is a good practice to release resources before entering the loop. This should help in preventing the deadlock issue as described.
  • 3987-3989: The loop iterates over shutdown_results and calls self.finish_close_channel(shutdown_result) for each item. Ensure that finish_close_channel can handle all possible states of shutdown_result that may occur, especially since funding_batch_states has been dropped just before.

lightning/src/ln/shutdown_tests.rs Outdated Show resolved Hide resolved
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@wpaulino wpaulino left a comment

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LGTM but CI needs fixing

When handling calls to `batch_funding_transaction_generated` which
were missing outputs for one of the batch channels, we'd previously
deadlock when trying to clean up the now-closed channels. This
fixes that and adds a new test case for it.

Found by the full_stack_target fuzzer.
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@coderabbitai coderabbitai bot left a comment

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Review Status

Actionable comments generated: 0

Configuration used: CodeRabbit UI

Commits Files that changed from the base of the PR and between 6b0ba8c and 983ca37.
Files selected for processing (2)
  • lightning/src/ln/channelmanager.rs (1 hunks)
  • lightning/src/ln/shutdown_tests.rs (3 hunks)
Files skipped from review as they are similar to previous changes (2)
  • lightning/src/ln/channelmanager.rs
  • lightning/src/ln/shutdown_tests.rs

@TheBlueMatt TheBlueMatt added this to the 0.0.121 milestone Jan 22, 2024
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Gonna go ahead and land this since the non-test diff is incredibly trivial and we should get to releasing.

@TheBlueMatt TheBlueMatt merged commit 15c9f5b into lightningdevkit:main Jan 22, 2024
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2 participants