{
  "finding_id": "DF-3718",
  "status": "inconclusive",
  "reproduced": 0,
  "impact": "none",
  "confidence": "certain",
  "verdict": "Source-certain, hardware-gated (DF-3680/DF-3714 family): mxge_tx_done (if_mxge.c:2364-2415) walks the TX completion ring toward mcp_idx = (int)send_done_count, the NIC-DMAd firmware stats counter (read :2695/:2767/:2844, passed :2700/:2770/:2847), with no bound against tx->req. A counter ahead of pkt_done unloads dmamaps and frees mbufs of still-queued descriptors (device DMA-after-free); a counter that never matches pkt_done (which freezes once a full revolution leaves every info[].m NULL) spins forever in interrupt context holding tx->tx_serialize and, on MSI/legacy, main_serialize - permanent interface/kernel-thread wedge. Guest lacks Myricom hardware; not runtime-testable (inconclusive per family convention).",
  "exploit_chain": "",
  "evidence": "findings/poc/DF-3718/VERDICT.md; fix.diff (occupancy guard, git-apply clean); env.txt",
  "kernel_refs": [
    "sys/dev/netif/mxge/if_mxge.c:2369",
    "sys/dev/netif/mxge/if_mxge.c:2381",
    "sys/dev/netif/mxge/if_mxge.c:2695",
    "sys/dev/netif/mxge/if_mxge.c:2770",
    "sys/dev/netif/mxge/if_mxge.c:2847"
  ],
  "poc_changes": "No seed PoC; hardware-gated.",
  "attempts": 1,
  "guest_uname": "DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64",
  "runtime_sec": 30,
  "guest_dirty": 0,
  "build_cmd": "n/a (hardware-gated)",
  "run_cmd": "n/a (hardware-gated)",
  "code_hash": "",
  "notes": "Failure mode is DoS/DMA-after-free on hostile-device premise; idx stays masked so no host-side OOB write.",
  "recommended_fix": "Guard the walk with ring occupancy: if (tx->done >= tx->req) break (warn), before consuming the next slot.",
  "fix_status": "not_testable",
  "fix_baseline_reproduced": 0,
  "fix_patched_reproduced": 0,
  "fix_verdict": "fix.diff git apply --check clean; not buildable without mxge hardware.",
  "fix_evidence": "findings/poc/DF-3718/fix.diff"
}