CVE-2022-47016: tmux, backport upstream fix (no version bump)

[jasonodoom]

⚠️ EXPERIMENTAL source-backport — NOT a version bump

This PR authors the upstream fix as an in-tree patch against the current nixpkgs version (no version bump). An agent generated it; a cross-family reviewer verified it transcribes the upstream commit, and a cert proved the bundled reproducer goes red→green. A human maintainer must still confirm sufficiency before merging:

• This applies the COMPLETE upstream fix, not one of several required commits.
• The backported hunk matches the upstream fix commit(s):
  • tmux/tmux@e867528
• Reviewed the cert evidence (reproducer red→green) for CVE-2022-47016.

Opened as a draft deliberately — mark Ready-for-review only after the boxes above are checked.

---

Evidence: CVE-2022-47016 (human-review-required) trace bundle 7fda15d2c893efd9

• Rekor entry: https://rekor.sigstore.dev/api/v1/log/entries?logIndex=2727301675
• Workflow identity: https://github.com/Ad-Astra-Computing/trace/.github/workflows/steward.yml@refs/heads/main
• OIDC issuer: https://token.actions.githubusercontent.com
• Cert run: https://github.com/Ad-Astra-Computing/trace/actions/runs/33973880496
• nixpkgs rev: 2355d599ca4dd683c33365f68c3a2f41fd6af68d

Verify locally

gh run download <run-id> --name steward-smoke-<bundle> --dir ./artifact
trace bundle verify ./artifact  # bundle_id=7fda15d2c893efd9

Generated by trace.

[jasonodoom]

Comparison against the upstream fix

Transcription lane (this PR's payload). The added and removed code lines of the embedded patch (control.c, file.c, window.c) are identical to the upstream fix commit tmux e8675282, normalized for whitespace. The cross-family Reviewer attested this; the check here was recomputed independently against the bundle's upstream-fix.patch. The Linux cert (trace run 33973880496) built tmux at the pinned revision with and without the patch: the unpatched arm fired the discriminator, the patched arm was clean.

Blind-authoring lane (separate measurement, not this payload). When the same CVE was given to claude-opus-4-8 with only the vulnerability description and the pre-fix source, never the upstream patch, the graded result against the human fix was PARTIAL: it patched the NULL return in control.c but missed the same check in file.c and window.c. Report: trace data/reports/authoring-accuracy-vs-human-2026-09-04.json.

The gap between the two lanes is the case for the gate. The Reviewer's line-level comparison against the upstream fix is what turns a partial blind fix into a complete backport before anything reaches a PR.