fix: Check command deadlocks on corrupted DB with page cycles#1202
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Abzaek wants to merge 1 commit into
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fix: Check command deadlocks on corrupted DB with page cycles#1202Abzaek wants to merge 1 commit into
Abzaek wants to merge 1 commit into
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When a database has a corrupt page structure with cycles (e.g., a branch page referencing an ancestor), recursivelyCheckPage enters infinite recursion, causing Check() to never complete. Fix: detect cycles by checking if the page ID is already in the reachable set before recursing. If already reachable, report the cycle and return. Fixes etcd-io#877
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[APPROVALNOTIFIER] This PR is NOT APPROVED This pull-request has been approved by: Abzaek The full list of commands accepted by this bot can be found here. DetailsNeeds approval from an approver in each of these files:Approvers can indicate their approval by writing |
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Thanks for your contribution. Do you have logs shows reproduction of this bug ? Also would you mind adding test cases practicing this case ? |
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Summary
The
Check()command deadlocks (infinite recursion) when the database has a corrupted page structure containing cycles — e.g., a branch page pointing to an ancestor.Root Cause
recursivelyCheckPage()traverses the page tree without any cycle detection. Thereachablemap exists but is only used after traversal for reporting unreachable/freed pages — it is never checked during traversal. A corrupted page pointing back to an ancestor causes unbounded recursion.Impact
This affects all etcd users running snapshot status/check on potentially corrupted databases. The
etcdctl snapshot statuscommand hangs forever, making recovery impossible.Fix
Check if the page ID is already in the
reachablemap before recursing. If it is, emit an error and return instead of recursing infinitely.Fixes #877