# DF-1411 — 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

sysctl_backlight_handler (:1814): conn_state=connector->base.state captured before modeset lock. :1829 sysctl_handle_int sleeps (user copy). :1835 drm_modeset_lock then intel_panel_set_backlight(conn_state,...). Concurrent atomic modeset frees old state via drm_atomic_state_default_clear. Stale conn_state->connector deref → UAF. CTLFLAG_ANYBODY (unprivileged) — but requires i915 hardware.

**Source:** `sys/dev/drm/i915/intel_panel.c:1814, 1829, 1835`

## Why it cannot be reproduced on this guest

HW-gated. i915.ko requires Intel integrated graphics. No Intel GPU in QEMU guest.

## Phase 6: Escalation Assessment

This is a **HW-gated GPU module (i915 backlight)** 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

Move conn_state capture inside the modeset lock section (after drm_modeset_lock, before intel_panel_set_backlight).

**Fix description:** Capture conn_state under drm_modeset_lock instead of before sysctl_handle_int sleep.

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)