{
  "finding_id": "DF-4877",
  "status": "untested",
  "reproduced": 0,
  "impact": "none",
  "confidence": "certain",
  "verdict": "afd_strategy() never bounds-checks bio_offset against mediasize (and the raw cdev path applies no clamp \u2014 bounds_check_with_mediasize() is dm-only), while narrowing the block number to u_int32_t lba and a 32-bit CDB LBA: any I/O at >= 2^32 sectors (2 TiB @512B) that must fail with EINVAL silently wraps onto low LBAs, so beyond-end writes clobber the start of the medium. Certain by construction; not runnable on a guest without ATAPI direct-access hardware.",
  "exploit_chain": "raw open /dev/afd0 -> pwrite at offset >= 2 TiB (legitimately out-of-range) -> lba = (offset/sectorsize) mod 2^32 (atapi-fd.c:258) -> ATAPI_WRITE_BIG CDB with wrapped LBA (atapi-fd.c:277-280) -> silent write to low blocks instead of EINVAL",
  "evidence": "VERDICT.md (trace: no clamp in strategy; dm-only bounds helper; ad keeps u64 lba); README.md",
  "kernel_refs": [
    "sys/dev/disk/nata/atapi-fd.c:241",
    "sys/dev/disk/nata/atapi-fd.c:258",
    "sys/dev/disk/nata/atapi-fd.c:277",
    "sys/kern/subr_disk.c:1458",
    "sys/dev/disk/dm/device-mapper.c:400",
    "sys/dev/disk/nata/ata-disk.c:299"
  ],
  "poc_changes": "n/a \u2014 source-trace finding; hardware blocker shared with DF-4874",
  "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": 0,
  "guest_dirty": 0,
  "build_cmd": "",
  "run_cmd": "",
  "code_hash": "",
  "notes": "Correctness/data-integrity class (raw device already grants full medium to opener), same size lie family as DF-4798; kept Low for that reason.",
  "recommended_fix": "reject bio_offset/end beyond mediasize with EINVAL before building the CDB in afd_strategy()",
  "fix_status": "not_testable",
  "fix_baseline_reproduced": 0,
  "fix_patched_reproduced": 0,
  "fix_verdict": "No afd hardware on guest; fix adds the missing media-bounds rejection with bounds_check_with_mediasize()-equivalent semantics",
  "fix_evidence": "fix.diff (git apply --check OK)"
}