gh-154709: Fix out-of-bounds access in dict reverse iterator - #154721
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serhiy-storchaka merged 5 commits intoJul 29, 2026
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needs backport to 3.13
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
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Thanks @BHUVANSH855 for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15. |
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GH-154888 is a backport of this pull request to the 3.15 branch. |
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GH-154889 is a backport of this pull request to the 3.14 branch. |
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GH-154890 is a backport of this pull request to the 3.13 branch. |
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Summary
Fix an out-of-bounds access in
dictreviter_iter_lock_held()when a reverse dictionary iterator is used after the underlying dictionary is cleared and modified.The fix adds bounds checks before indexing into the dictionary's storage for both split-table and combined-table dictionaries. If the iterator's position is no longer valid, it now exits cleanly instead of accessing invalid memory.
A regression test has also been added to verify that this scenario no longer results in a crash.
Testing
./python -m test test_dict./python -m test test_gc./python -m test test_builtin./python -m test test_dict test_gc test_builtinreversed(dict)can read out of bounds and segfault (dictreviter_iter_lock_held) #154709