⬢ DragonFlyBSD Kernel Audit
DF-3648 / verdict.json
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{
  "finding_id": "DF-3648",
  "status": "inconclusive",
  "reproduced": 0,
  "impact": "none",
  "confidence": "certain",
  "verdict": "Source-certain div-by-zero, radeon/ci twin of DF-3613 (si) / DF-3622 (amdgpu ci). radeon_atombios_get_clock_info stores usMemoryReferenceClock (DCE4+ path, radeon_atombios.c:1216-1218; CI is DCE8) into rdev->clock.mpll.reference_freq with no sanity check; a crafted FirmwareInfo with that field 0 leaves reference_freq == 0. ci_calculate_mclk_params reads it (ci_dpm.c:2865) and divides tmp = freq_nom / reference_clock (2872) inside the caps_mclk_ss_support block - #DE panic. The sclk path is affected indirectly: clk_s = reference_clock * 5 / (ref_div * ss.rate) evaluates to 0 when reference_clock == 0, and the very next line divides by it (clk_v = ... / (clk_s * 10000), ci_dpm.c:3228) - div-by-zero again. On-guest harness section [C] proved 300000/0 faults with SIGFPE. Kernel path unreachable on this GPU-less guest; inconclusive overall.",
  "exploit_chain": "Crafted VBIOS whose FirmwareInfo reports usMemoryReferenceClock (or the pre-DCE4 usReferenceClock) as 0, with the SS info table present so caps_*_ss_support is set -> u32 divide by zero at DPM table population -> panic at load. DoS only.",
  "evidence": "VERDICT.md (full source trace); harness.c + run.log/run.2.log section [C] (SIGFPE (kernel: #DE panic)); env.txt (guest has no AMD GPU: pciconf 0x1002 count=0, /dev/dri absent, no drm kld); fix.diff",
  "kernel_refs": [
    "sys/dev/drm/radeon/ci_dpm.c:2865",
    "sys/dev/drm/radeon/ci_dpm.c:2872",
    "sys/dev/drm/radeon/ci_dpm.c:3203",
    "sys/dev/drm/radeon/ci_dpm.c:3227",
    "sys/dev/drm/radeon/ci_dpm.c:3228",
    "sys/dev/drm/radeon/radeon_atombios.c:1216",
    "sys/dev/drm/radeon/radeon_atombios.c:1221"
  ],
  "poc_changes": "n/a \u2014 no seeded PoC for pass-2; harness written fresh (models the exact kernel types; divisors made volatile so -O2 cannot fold the #DE)",
  "attempts": 2,
  "guest_uname": "DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026     root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64",
  "runtime_sec": 45,
  "guest_dirty": 1,
  "build_cmd": "cc -O2 -Wall -o harness harness.c",
  "run_cmd": "./harness",
  "code_hash": "af83fc943c96cc840bab14bf99787f6e37c43ec42b624d998c2461cc2dad15f2",
  "notes": "pass 2 radeon/ci_dpm.c; twins: DF-3613/DF-3622. Guest virtio-only per task; harness scratch files under /root removed.",
  "recommended_fix": "Skip SS programming (or fail DPM init) when rdev->clock.{mpll,spll}.reference_freq is 0.",
  "fix_status": "not_testable",
  "fix_baseline_reproduced": 0,
  "fix_patched_reproduced": 0,
  "fix_verdict": "Fix validation would require a CI-class GPU with a crafted VBIOS (baseline panic/corruption) and a single-fix kernel build; the audit guest is virtio-only, so the fix is source-reviewed only (fix.diff).",
  "fix_evidence": "fix.diff in this pack; not applied to sys/ (read-only audit target)."
}