# VERDICT — DF-3743

**Status**: inconclusive (source-certain; harness-reproduced arithmetic; kernel path unreachable on this guest)
**reproduced**: 0 (in-kernel) — harness demonstration: YES
**Impact on real hardware**: Medium — CWE-369 Divide By Zero

## Finding
Parse-side root of the SS-rate divide-by-zero family (sink side already filed as DF-3621 [si] / DF-3647 [ci]). radeon_atombios_get_asic_ss_info() returns success with ss->rate==0 via three distinct paths: v1 stores usSpreadRateInKhz verbatim (:1546); v2/v3 store usSpreadRateIn10Hz then integer-divide by 100 for ENGINE/MEMORY SS (:1569, :1594) so any value <100 truncates to 0. radeon_atombios_get_ppll_ss_info() never assigns rate at all (memset at :1390 remains) yet returns true (:1400-1413). Sinks divide by ss.rate: si_dpm.c:4833 and ci_dpm.c:3229 (clk_s = reference_clock * 5 / (reference_divider * ss.rate)). Harness on guest: v3 parse of usSpreadRateIn10Hz=50 -> rate=0 -> verbatim sink expression -> SIGFPE (exit 42). Kernel path unreachable on this guest.

## Why not reproduced in-kernel
The QEMU guest is virtio-only (no AMD GPU): `pciconf -l` shows no 1002 device;
`kldstat` shows radeon not loaded. `/boot/kernel/radeon.ko` exists (the vulnerable code ships in
the default install) but cannot attach, so radeon_atombios.c parse paths never execute here.
All conclusions are source-level (path:line above) plus the on-guest harness (harness_ssrate.c).

## Harness result
Command: ./run.sh (after ./build.sh)
Expected/observed: ss.rate=0 after parse; sink division SIGFPE at stage 1, exit_code=42
Full logs: build.log, run.log.

## Impact / exploit chain
crafted ASIC_InternalSS_Info (v2/v3 rate<100, or v1 rate=0) or PPLL_SS_Info table -> parse returns true with rate=0 -> DPM enable programs SS -> divide-by-zero -> #DE kernel panic

## Fix
treat rate==0 entries as invalid (return false / skip) — fix.diff.

## Honest notes
- DF-3743 does NOT re-report pass-1 findings DF-1198/1199/1200 (power-table state_index mismatch,
  asic_ss_info underflow, power-table indices) — different functions/tables/fields.
- fix validation not possible on this guest (no hardware); fix.diff is source-authored only.

## Fix status (batch validation)
Applied with the 36 sibling fix.diffs of this batch in findings/poc/_batch41/all_fixes.patch; single in-guest `make -j6 nativekernel KERNCONF=X86_64_GENERIC` completed RC=0 with zero errors under -Werror (full log: findings/poc/_batch41/fix_build8.log). Behavior A/B intentionally skipped for this Info-tier item.