{
 "finding_id": "DF-3034",
 "status": "not_reproduced",
 "reproduced": 0,
 "impact": "none",
 "confidence": "certain",
 "verdict": "Line-accurate confirmation; runtime demonstration deliberately not attempted (the mismatched-device-buffer precondition is prevented by getblk/breadcb acquiring at exactly obp->b_bufsize, and the path requires non-default hammer_double_buffer=1). The only gate before bcopy(bp->b_data, ..., obp->b_bufsize) is the KKASSERT at hammer_io.c:1676 - compiled out on production - and the CRC check at :1658-1664 reads obp->b_bufsize bytes from bp->b_data with the same unguarded assumption. Fix adds an explicit runtime size gate (B_ERROR/EIO short-circuit before the CRC condition); compiled in the F40FIX build (HAMMER in kernel).",
 "exploit_chain": "",
 "evidence": "VERDICT.md with path:line citations; run.log where a live demo exists; fix.diff",
 "kernel_refs": [
  "sys/vfs/hammer/hammer_io.c:1658",
  "sys/vfs/hammer/hammer_io.c:1676",
  "sys/vfs/hammer/hammer_io.c:1677"
 ],
 "poc_changes": "n/a - no PoC (size match guaranteed by getblk/breadcb on this guest)",
 "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": "explicit bp->b_bufsize >= obp->b_bufsize runtime gate failing with EIO, ahead of CRC + bcopy",
 "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)"
}