# DF-1438 — Verification Verdict

## Verdict: CONFIRMED-BY-SOURCE-TRACE (HW-gated)

**Status:** inconclusive (HW-gated / not reachable as unprivileged maxx)
**Impact:** none (cannot reproduce on QEMU guest — no GPU/HW, or root/operator-only)
**Confidence:** certain (source-trace confirmed bug is real)

## Mechanism

sumo_calculate_bsp (:323): pasi=65535*100/high_clk. high_clk from ps->levels[num_levels-1].sclk or boost_pl.sclk, both VBIOS-derived. sclk=0 → div-by-zero #DE panic on DPM state transition.

**Source:** `sys/dev/drm/radeon/sumo_dpm.c:323`

## Why it cannot be reproduced on this guest

HW-gated. radeon.ko requires Sumo/Trinity ASIC. No GPU in QEMU guest.

## Phase 6: Escalation Assessment

This is a **HW-gated GPU module (radeon DPM Sumo)** finding. The primitive is not reachable from the
unprivileged maxx user on this guest (no hardware / module not loaded / root-only device).
No escalation chain is possible because the trigger path is not exercisable.

For GPU findings: the module (radeon.ko/amdgpu.ko/i915.ko) is a loadable module not
present in the GENERIC kernel and requires actual GPU hardware absent from the QEMU guest.
For root/operator findings: the device node is mode 0600 or 0640 root:operator, and maxx
(uid 1001) has no operator group membership.

## Fix

Check high_clk != 0 before division; return early if 0.

**Fix description:** Add `if (high_clk == 0) return;` guard before division.

The full git-apply-able diff is in `fix.diff`. It applies cleanly to the audit source tree
and compiles as part of the kernel build (validated via `make nativekernel` rc=0).

## Classification

- **status:** inconclusive
- **reproduced:** 0
- **impact:** none
- **fix_status:** not_testable (HW-gated: PoC cannot run on guest; diff applies + compiles verified)