# VERDICT -- DF-1366

## Verdict: INCONCLUSIVE at runtime; source bug CONFIRMED; fix COMPILE-VALIDATED

**Citations confirmed:**
  - sys/dev/drm/amd/powerplay/smumgr/vegam_smumgr.c:1217
  - sys/dev/drm/amd/powerplay/smumgr/vegam_smumgr.c:1220
  - sys/dev/drm/amd/powerplay/smumgr/vegam_smumgr.c:1221

### Is the bug real? -- YES (source trace)

vegam_populate_smc_vce_level() sets `table->VceLevelCount = (uint8_t)(mm_table->count)`
    then loops `count < VceLevelCount` writing table->VceLevel[count]. The VceLevel[]
array is fixed at SMU75_MAX_LEVELS_VCE = 8 (smu75_discrete.h:293). mm_table->count
comes from VBIOS ucNumEntries (u8, 0-255) with no clamp, so count>8 overflows into
the following fields of SMU75_Discrete_DpmTable (and into vegam_smumgr fields such
as power_tune_defaults). Reached during powerplay init.

### Can it be reproduced on this guest? -- NO (hardware-gated)

No AMD GPU in PCI list (only QEMU stdvga 0x11111234); amdgpu.ko is not loaded and would not attach without the HW.

The amdgpu driver is a loadable module only (NOT in `X86_64_GENERIC`), is not loaded, and cannot be `kldload`'d by an unprivileged user (kldload is root-only). Even loaded, it would not attach without the hardware.
Therefore the vulnerable code is unreachable at runtime here. Because the sinks are device-integrated parsers / DRM ioctls / DMA-supplied indices / hardware-dependent paths, no userspace harness on this guest can exercise them. This is the documented valid hard-blocker "unreachable at runtime + no feasible harness"; the bug is a real latent defect with the live trigger conditions noted above.

### No escalation chain (and why that is correct here)
There is no memory-corruption primitive to escalate on this guest: the corruption sinks live entirely inside the not-attached driver behind hardware that is absent. The escalation work the audit expects (slab groom -> victim -> uid0) presupposes a reachable write primitive; here there is none on the guest. The deliverable is therefore the confirmed root-cause + a compile-validated fix.

### Fix (fix.diff) -- authored and COMPILE-VALIDATED
Clamped the count using the same ternary pattern already used elsewhere in the
file for pcie-link levels: `VceLevelCount = (uint8_t)((SMU75_MAX_LEVELS_VCE <
mm_table->count) ? SMU75_MAX_LEVELS_VCE : mm_table->count)`. (matches finding
proposal.)

The fix was applied to in-guest `/usr/src` (all hunks applied cleanly) and the
module was rebuilt with the kernel's `-Werror` flags: `cd /usr/src/sys/dev/drm/amdgpu && KERNCONF=X86_64_GENERIC SYSDIR=/usr/src/sys make -m /usr/src/share/mk` => rc=0 (see `build_fix.log`). No warnings or errors in the patched translation unit. The runtime before/after of the bug cannot be tested on this guest (no hardware), so fix_status is `not_testable` (diff applies + compiles; code path traced closed).

### Why not `not_reproduced` (false-positive)?
This is NOT a false positive. The cited `sys/` code is genuinely missing the guard / has the overflow / has the unclamped loop -- verified by reading the source. It is a real bug that is simply out of reach of this particular (driverless) QEMU guest.