fix(mm): close TOCTOU race in _restore_incomplete_installs#9142
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fix(mm): close TOCTOU race in _restore_incomplete_installs#9142
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The restore path snapshotted active sources under the lock, then released the lock and iterated tmpdirs against the stale snapshot. A foreground import_model call landing during iteration could append a job the loop never saw, leading to a duplicate enqueue and a FileNotFoundError when the second download tried to rename the .downloading file the first had already moved. Move the membership check inside the lock immediately before the append so check-and-append is atomic. Fixes #9141. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
_restore_incomplete_installssnapshotted active sources under the lock, then iterated tmpdirs against the stale snapshot. A foregroundimport_modelcall landing during iteration could be missed, the same source enqueued twice, and the second download would fail withFileNotFoundErrorwhen trying to rename the.downloadingfile the first download had already moved._install_jobs.append(job)so check-and-append is atomic. Duplicate-tmpdir suppression within a single restore pass stays outside the lock since it doesn't race againstimport_model.Fixes #9141.
Test plan
pytest tests/app/services/model_install/test_model_install.py::test_simple_download— ran 10× consecutively, all pass (was flaky ~30–50% onmain)pytest tests/app/services/model_install/— 31/31 pass🤖 Generated with Claude Code