PoC verification

Evidence pack

findings/poc/DF-1439 · 8 files

File	Type	Description	Size
fix.diff	suggested-fix	Add `if (num_max_dpm_entries == 0) return lower_limit;` guard before entries[] access.	491 B	view raw
VERDICT.md	verdict	Full source-trace analysis	1.8 KB	↓ raw
build.sh	build-script	Kernel build validation	534 B	view raw
run.sh	run-script	PoC runner (not runnable on guest)	454 B	view raw
fix_build.log	build-log	Full kernel build output (make nativekernel rc=0)	5.6 MB	↓ download
env.txt	environment	Guest environment	277 B	view raw
../fix_build_combined.log	build-log	Combined 41-finding kernel build (rc=0, -Werror clean)	5.6 MB	↓ download
../fix_build_summary.txt	build-summary	Summary of the combined 41-finding kernel build	826 B	view raw

VERDICT.md verdict Full source-trace analysis

↓ download raw

DF-1439 — Verification Verdict

Verdict: CONFIRMED-BY-SOURCE-TRACE (HW-gated)

Status: inconclusive (HW-gated / not reachable as unprivileged maxx) Impact: none (cannot reproduce on QEMU guest — no GPU/HW, or root/operator-only) Confidence: certain (source-trace confirmed bug is real)

Mechanism

sumo_get_valid_engine_clock (:1042): entries[num_max_dpm_entries-1]. If num_max_dpm_entries==0 (VBIOS all-zero sAvail_SCLK) → entries[(u32)-1] → ~32GB OOB read → page fault panic.

Source: sys/dev/drm/radeon/sumo_dpm.c:1042

Why it cannot be reproduced on this guest

HW-gated. radeon.ko requires Sumo/Trinity ASIC. No GPU in QEMU guest.

Phase 6: Escalation Assessment

This is a HW-gated GPU module (radeon DPM Sumo) finding. The primitive is not reachable from the unprivileged maxx user on this guest (no hardware / module not loaded / root-only device). No escalation chain is possible because the trigger path is not exercisable.

For GPU findings: the module (radeon.ko/amdgpu.ko/i915.ko) is a loadable module not present in the GENERIC kernel and requires actual GPU hardware absent from the QEMU guest. For root/operator findings: the device node is mode 0600 or 0640 root:operator, and maxx (uid 1001) has no operator group membership.

Fix

Return lower_limit when num_max_dpm_entries==0.

Fix description: Add if (num_max_dpm_entries == 0) return lower_limit; guard before entries[] access.

The full git-apply-able diff is in fix.diff. It applies cleanly to the audit source tree and compiles as part of the kernel build (validated via make nativekernel rc=0).

Classification

status: inconclusive
reproduced: 0
impact: none
fix_status: not_testable (HW-gated: PoC cannot run on guest; diff applies + compiles verified)

Confirmed kernel references

Detail

Exploit chain

none (wild OOB read / page fault — read-only primitive but causes panic (DoS). HW-gated: radeon DPM on Sumo/Trinity. Not reachable from QEMU.)

Evidence (decisive lines)

Source trace: sumo_dpm.c:1042 'return pi->sys_info.sclk_voltage_mapping_table.entries[pi->sys_info.sclk_voltage_mapping_table.num_max_dpm_entries - 1].sclk_frequency' — if num_max_dpm_entries==0, index wraps to (u32)-1.

PoC changes

Authored fix.diff: add 'if (num_max_dpm_entries == 0) return lower_limit;' guard before entries[] access.

Verified recommended fix

Return lower_limit when num_max_dpm_entries==0. matches finding proposal. Full diff in findings/poc/DF-1439/fix.diff.

Verdict

CONFIRMED BY SOURCE TRACE. sumo_get_valid_engine_clock at sumo_dpm.c:1042: entries[num_max_dpm_entries-1]. If num_max_dpm_entries==0 (VBIOS all-zero sAvail_SCLK) → entries[(u32)-1] → ~32GB OOB read → page fault panic. Bug is real but HW-gated: radeon.ko requires Sumo/Trinity ASIC.

Wild OOB read in sumo_get_valid_engine_clock when num_max_dpm_entries==0

Summary

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