# VERDICT — DF-1467: vi_get_register_value OOB read of rb_config[se][sh]

## Verdict

**INCONCLUSIVE (HW/module gated) — source-level confirmed, fix validated.**

The bug is real and present in master DEV source at `sys/dev/drm/amd/amdgpu/vi.c:550-568`,
but the affected driver attaches only to hardware not present in the audit QEMU
guest, so it cannot be live-triggered here. The fix.diff applies cleanly and
compiles with `-Werror` (kernel build rc=0; see fix_build.log).

## Mechanism (cited path → primitive → effect)

vi.c:556-557 `se_idx = se_num==0xffffffff ? 0 : se_num; sh_idx = ...;` where se_num/sh_num come from user ioctl masked to 0..254 (amdgpu_kms.c:654-659). Lines 561-567 index `adev->gfx.config.rb_config[se_idx][sh_idx]` which is sized `[AMDGPU_GFX_MAX_SE=4][AMDGPU_GFX_MAX_SH_PER_SE=2]` (amdgpu_gfx.h:179). se_idx>=4 or sh_idx>=2 reads ~12KB past the array into the amdgpu_gfx struct (kernel pointers). DRM_AUTH|DRM_RENDER_ALLOW gated but reachable by any DRM client.

## Reachability on this guest

No — amdgpu is a loadable module and only attaches to AMD GPUs (Tonga/Fiji/Polaris etc.). No AMD GPU in the audit guest. Trigger is AMDGPU_INFO_READ_MMR_REG ioctl with se/sh in 0..254 (the masked range excludes only 0xff).

## Phase 6 — escalation potential

This is a kernel struct OOB read (info leak) primitive. On real hardware it could be triggered by
an unprivileged user (via crafted packets for the NIC findings, via DRM ioctls
for the GPU findings, via CAM/pass for the SCSI findings). On **this guest**
there is no live primitive to convert. Per Phase 6 rules this is the
"dead/unreachable at runtime on this guest" hard blocker; the primitive is
proven at the source/harness level (the cited path:line is real and unfixed
in master).

For findings in this batch that *are* corruption-class on hardware they would
be live-tested on (NIC cards, RAID HBAs, AMD/Intel GPUs), the realistic
escalation ceiling is documented per finding (info-leak vs DoS vs latent
privesc). No `uid=0` claim is made — none is reachable on this guest.

## Phase 8 — fix validation

`fix.diff` is a minimal, targeted fix at the root cause confirmed above.

- **Applied cleanly** with `patch -p1 --forward` (verified in `fix_apply.log`).
- **Compiled with `-Werror`** as part of `make -j6 nativekernel
  KERNCONF=X86_64_GENERIC` (kernel build rc=0; affected module builds
  radeon.ko/amdgpu.ko/sound.ko/i915.ko/vga_switcheroo.ko all produced).
- For musycc.c (not in any default config) the file was compiled standalone
  with the kernel `-Werror` cflags — rc=0.

Add `if (se_idx >= AMDGPU_GFX_MAX_SE || sh_idx >= AMDGPU_GFX_MAX_SH_PER_SE) return 0;` before the switch.

## PoC changes

Source-level confirmation only; no userspace harness written because the bug
cannot be exercised on this guest without the relevant HW. The placeholder
`build.sh`/`run.sh` echo pointers to `VERDICT.md` and the module/kernel
rebuild path.