# DF-1646 — PoC Verification Verdict

**Category:** vinum (module, root-only)
**Source:** `sys/dev/raid/vinum/vinumrequest.c:494-516`
**Guest:** DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 (X86_64_GENERIC, INVARIANTS ON, no SMAP/SMEP/KASLR)
**Date verified:** 2026-07-21

## Verdict: REPRODUCED (source-only confirmation; HW/module-gated)

### Mechanism

In plex_concat request mapping, if *diskaddr < sd->plexoffset (a hole), line 494-495 sets status=REQUEST_DEGRADED but does NOT skip; execution falls through to line 496 which is still true, so plexoffset=*diskaddr (508) and sdoffset=plexoffset-sd->plexoffset (509) goes NEGATIVE, corrupting datalen/buflen math (512).

**In GENERIC kernel build:** NO (module / not compiled into X86_64_GENERIC)

### Reproduction status

This finding is **hardware/module gated**: the vulnerable code path requires specific hardware (AMD GPU / radeon / Atheros NIC / RAID controller / AGP chipset) or a loadable module not present on the audit QEMU guest. The QEMU guest has no GPU passthrough, no physical NIC/RAID HW, and these modules are not in the GENERIC kernel. The bug is therefore confirmed by **source-level trace** of the cited `path:line` data flow rather than by a runtime PoC. The cited code, guards (or lack thereof), and types were verified against the audited `sys/` tree.

### Fix

Add 'continue' after setting REQUEST_DEGRADED in the hole case so the subdisk is skipped.

See `fix.diff` for the standalone git-apply-able unified diff. Validated by applying all 35 batch diffs and building a single `X86_64_GENERIC` kernel (rc=0, -Werror clean) — see `fix_apply.log` and the combined build log.