wallet: detect cycles in BDB page traversal during migration #34946

1. 
   instagibbs commented at 10:43 pm on March 28, 2026: member

   The read-only BDB parser follows page chains without tracking visited pages. A crafted BDB file with circular references causes an infinite loop with unbounded memory growth, crashing the process.

   Add visited-page sets to both the BTree DFS traversal and overflow page chain traversal, throwing on the first revisited page.

   Script to craft a .dat file which demonstrated the issue (should run and suck up memory until OOM): https://gist.github.com/instagibbs/f92c17c34bfefa4aa391cb2b9c6306de

   Issue discovered/demo’d/fixed by Claude.

2. wallet: detect cycles in BDB page traversal during migration

   The read-only BDB parser follows page chains without tracking
   visited pages. A crafted BDB file with circular references causes
   an infinite loop with unbounded memory growth, crashing the process.
   
   Add visited-page sets to both the BTree DFS traversal and overflow
   page chain traversal, throwing on the first revisited page.

   0bf2a12dd4
3. DrahtBot added the label Wallet on Mar 28, 2026
4. 
   DrahtBot commented at 10:43 pm on March 28, 2026: contributor

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   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #34959 (wallet: Enforce BDB btree levels and overflow item sizes by achow101)

   If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

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Wallet