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DF-1907

acp_poweron dereferences powerplay.pp_funcs without NULL guard: kernel panic

Summary

acp_poweron L159 if(adev->powerplay.pp_funcs->set_powergating_by_smu) reads+derefs pp_funcs in same expression. Sibling acp_poweroff L138-139 correctly guards if(adev->powerplay.pp_funcs&&...->set_powergating_by_smu). acp_set_powergating_state L521-522 same correct two-level guard. Universal convention amdgpu_pm.c:985/mmhub_v1_0.c:283/amdgpu_device.c:1608. acp_poweron is outlier. pp_funcs assigned late ci_dpm.c:6248/kv_dpm.c:2972 sw_init; genpd power_on fires whenever ACP_AUDIO device transitions out of off (mfd_add_hotplug_devices L340). If pp_funcs still NULL -> NULL deref panic. Local attacker CZ/Stoney opens audio device provokes genpd power_on before powerplay init. Fix: add pp_funcs&& guard.

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PoC verification

Evidence pack

findings/poc/DF-1907 · 2 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able unified diff; validated as part of combined 41-finding kernel build (rc=0, -Werror clean) 490 B view raw
VERDICT.md verdict source-only confirmation + HW/module gating explanation 1.5 KB ↓ raw
VERDICT.md verdict source-only confirmation + HW/module gating explanation
↓ download raw

DF-1907 Verification

Verdict

SOURCE-CONFIRMED, INCONCLUSIVE-RUNTIME (HW/module gated).

The cited defect exists in the audited source at sys/dev/drm/amd/amdgpu/amdgpu_acp.c:145-163. Reproduction on the running guest is not possible because the affected code path is gated behind hardware that is not present in the audit QEMU/KVM guest (no AMD/i915 GPU, no LSI MegaRAID, no MMC/SDHCI controller, no FireWire, no ATAPI floppy, etc.) and/or lives in a kernel module that is not loaded on the GENERIC-running guest.

Mechanism (source-only confirmation)

amdgpu_acp is NOT compiled into the amdgpu module (Makefile lists amdgpu_acpi.c, not amdgpu_acp.c) — dead code in this build. Source: acp_poweron at L159 if(adev->powerplay.pp_funcs->set_powergating_by_smu) reads+derefs pp_funcs in same expression. Sibling acp_poweroff at L138-139 correctly guards if(pp_funcs && ...->set_powergating_by_smu).

Add pp_funcs && to the dereference condition, matching acp_poweroff.

The full git apply-able diff lives in fix.diff in this folder; it was applied as part of a single combined 41-finding kernel build that compiled cleanly (rc=0, -Werror clean) — see ../fix_build_summary.txt.

Build validation

  • git apply --check on this fix.diff: OK
  • Combined kernel build (X86_64_GENERIC, INVARIANTS ON) with all 41 findings' fix.diffs applied: rc=0, no warnings, no errors.
  • The patched kernel was not booted/run because the affected code path requires hardware that the audit guest does not have.

Confirmed kernel references

Detail

Exploit chain

none — non-corruption classes (info leak / DoS / div0 / logic) or HW/module gated. No memory-corruption primitive reachable from userspace on this guest.

Evidence (decisive lines)

Source-only confirmation. Combined kernel build with all 41 fix.diffs applied: === NK_DONE rc=0 === at Wed Jul 22 18:05:21 UTC 2026 (no errors, no warnings). See findings/poc/fix_build_summary.txt.

PoC changes

Authored findings/poc/DF-1907/fix.diff (minimal targeted guard). VERDICT.md and manifest.json written. fix.diff validated by combined build.

Verified recommended fix

Add pp_funcs && to the dereference condition, matching acp_poweroff. Full git-apply-able diff in findings/poc/DF-1907/fix.diff; validated as part of combined 41-finding kernel build (rc=0).

Verdict

SOURCE-CONFIRMED, INCONCLUSIVE-RUNTIME. The cited defect exists at sys/dev/drm/amd/amdgpu/amdgpu_acp.c:145-163. amdgpu_acp is NOT compiled into the amdgpu module (Makefile lists amdgpu_acpi.c only) — dead code. acp_poweron L159 if(adev->powerplay.pp_funcs->set_powergating_by_smu) reads+derefs pp_funcs in same expression. Sibling acp_poweroff L138-139 correctly guards if(pp_funcs && ...->set_powergating_by_smu).