# DF-1403 — 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

cik_get_register_value (:1032-1043): se_idx/sh_idx from user ioctl AMDGPU_INFO_READ_MMR_REG (masked 0xff, range 0-254). rb_config[4][2] array (AMDGPU_GFX_MAX_SE=4, AMDGPU_GFX_MAX_SH_PER_SE=2). No bounds check. se_idx>=4 or sh_idx>=2 → OOB read of kernel heap past amdgpu_gfx_config. Each 4B value returned to user via AMDGPU_INFO ioctl (DRM_AUTH|DRM_RENDER_ALLOW). KASLR bypass + heap leak. Same bug exists in vi.c.

**Source:** `sys/dev/drm/amd/amdgpu/cik.c:1032-1043`

## Why it cannot be reproduced on this guest

HW-gated. amdgpu.ko requires CIK hardware (Bonaire/Hawaii/Kaveri). No AMD GPU in QEMU guest.

## Phase 6: Escalation Assessment

This is a **HW-gated GPU module (amdgpu CIK)** 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 se_idx < AMDGPU_GFX_MAX_SE && sh_idx < AMDGPU_GFX_MAX_SH_PER_SE before array access.

**Fix description:** Add bounds check se_idx < AMDGPU_GFX_MAX_SE && sh_idx < AMDGPU_GFX_MAX_SH_PER_SE before rb_config[][] access.

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)