# DF-2066 — VERDICT

**Verdict:** REPRODUCED (source-confirmed; HW/module-gated — not runtime-triggerable on this guest)
**Class:** Control-flow / missing completion (CWE-664)
**Impact ceiling:** dos
**Confidence:** likely

## Reproduction status

This finding is **HW/module-gated** and could not be triggered at runtime on the
audit guest. The guest has **no Atheros NIC, no AdvanSys HBA, no Intel i915 GPU,
no AMD Southern-Islands GPU, no LSI MegaRAID controller, and no loaded dm
device** (only `vtnet0`). The PoC therefore cannot reach the vulnerable path at
runtime here. The bug is instead **confirmed by line-by-line source tracing**
against the audited `sys/` tree (master DEV, the same commit the kernel was built
from) — the defect is real and deterministic *given the hardware/module*, which is
the standard bar for HW-gated driver findings.

## Mechanism (source-confirmed)

mfi_syspd_strategy() on controller->hw_crit_error (:249-252) or issuepend_done==0 (:254-257) sets bp->b_error=EBUSY and returns WITHOUT setting B_ERROR, WITHOUT setting b_resid, and WITHOUT calling biodone(). The bio is therefore never completed and the issuer blocks forever in an unkillable D-state. The correct completion pattern is 8 lines above for the NULL si_drv1 case (:240-246): b_error + B_ERROR + b_resid + biodone. issuepend_done is cleared during OCR (mfi_tbolt.c) and hw_crit_error is set on PCI-access failure during adapter reset -- both windows are live. Systemic twin in mfi_disk.c.

**Gating precondition:** LSI MegaRAID (mfi) controller in syspd (raw JBOD) mode + /dev/mfisyspdN access during controller fault/OCR

## Exploit chain

Not applicable — this finding is HW/module-gated on the audit guest (no
triggering hardware/module present), so no userspace-driven escalation chain can
be exercised here. Per AGENT.md Phase 6 the valid hard blocker that applies is
"vulnerable code path is reachable only on hardware/module absent from this
guest." The realistic impact ceiling for the bug itself is `dos` as
documented above (panic for the corruption-class bugs on default GENERIC with
INVARIANTS ON; dos for the I/O-wedge/stall bugs; none/graceful-fallback for the
validation-bypass and pure missing-check / resource-leak findings).

## Fix (authored, git-apply-able)

On the hw_crit_error and issuepend_done==0 paths in mfi_syspd_strategy(), set bp->b_flags |= B_ERROR, bp->b_resid = bp->b_bcount and call biodone(bio) before returning, mirroring the NULL-si_drv1 path.

The standalone diff is `fix.diff` in this directory. It applies cleanly to the
pristine audited source (`git apply --check` verified).

## Phase 8 — combined fix-build validation

All nine findings' fixes were applied together to a single in-guest source tree
and built with `make -j6 nativekernel KERNCONF=X86_64_GENERIC`. The DragonFly
kernel compile invokes `cc ... -Werror` on **every** translation unit, so this
is a true **-Werror** build.

- Result: **`=== NK_DONE rc=0 ===`** (full log: `fix_build.log`)
- Compiler errors in changed files: **0**
- Compiler warnings (entire tree): **0**
- Patched `kernel.stripped` sha256: `6086a989213ef7be890180f60edc0fd9827bf60efbc3ed8c969724746e250df6`
- Baseline (unpatched) kernel: `DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026`

Because the PoC is HW/module-gated, the fix could not be runtime A/B tested on
this guest (no way to trigger the bad behaviour on either the baseline or the
patched kernel). The fix is therefore classified **fix_status = not_testable**
(compile-validated + source-traced to close the cited path), which is the honest
result for HW-gated findings.

## Kernel references (verified during this trace)

- `sys/dev/raid/mfi/mfi_syspd.c:249`
- `sys/dev/raid/mfi/mfi_syspd.c:254`
- `sys/dev/raid/mfi/mfi_syspd.c:240`
- `sys/dev/raid/mfi/mfi_syspd.c:244`