{
 "finding_id": "DF-3245",
 "status": "not_reproduced",
 "reproduced": 0,
 "impact": "none",
 "confidence": "certain",
 "verdict": "Line-accurate confirmation; no runtime demonstration attempted because no in-tree caller can supply a negative unit (if_name2unit clamps, clone-on-open uses fff-allocated units; the one semi-reachable negative value, devfs_reference_ops id==-1 after the 255-ops-id limit, hits the chk/read path only). All three helpers compute chunk = unit/64 by C truncation and check only the upper bound: chk OOB-reads bitmap[-1] and evaluates 1UL << negative (UB), set OOB-WRITES below the allocation, put OOB-WRITES a set bit below the array (devfs_helper.c:141-210). Fix adds unit<0/chunk<0 guards at all three sites; compiled in the F40FIX build (devfs_helper.c is standard).",
 "exploit_chain": "",
 "evidence": "VERDICT.md with path:line citations; run.log where a live demo exists; fix.diff",
 "kernel_refs": [
  "sys/vfs/devfs/devfs_helper.c:141",
  "sys/vfs/devfs/devfs_helper.c:171",
  "sys/vfs/devfs/devfs_helper.c:201"
 ],
 "poc_changes": "n/a - no reachable negative caller",
 "attempts": 0,
 "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": "see build.sh",
 "run_cmd": "see run.sh",
 "code_hash": null,
 "notes": "",
 "recommended_fix": "reject unit<0 (and derived chunk<0) in chk/set/put",
 "fix_status": "compile_validated",
 "fix_verdict": "fix.diff applied in the F40FIX verification kernel build (RC=0, zero -Werror errors); no runtime A/B for this item (line-certain hardening)"
}