DF-1169

Integer underflow sends 0xFFFFFFFF PCIe DPM level to SMC firmware

Summary

smu7_force_clock_level at :4384-4393: tmp=mask&pcie_dpm_enable_mask. If tmp==0: fls(0)=0, ffs(0)=0, inequality false, sends fls(0)-1=0xFFFFFFFF to PPSMC_MSG_PCIeDPM_ForceLevel. mask==0 check at :4366 does NOT cover zero intersection. Root-only sysfs. GPU hang/firmware fault. Fix: if(!tmp) return -EINVAL.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U:C:N/I:N/A:H
CWE: CWE-191 Integer Underflow
File: sys/dev/drm/amd/powerplay/hwmgr/smu7_hwmgr.c
Lines: 4382-4393
Area: dev
Discovered: 2026-07-15
Updated: 2026-07-15

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: certain
Tested: 2026-07-25 10:25:05
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-25 10:25:05
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1169/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1169 · 3 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-1169	619 B	↓ raw
fix.diff	suggested-fix	Guard tmp==0 before fls(tmp) to prevent underflow	445 B	view raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-1169

↓ download raw

DF-1169 Verification Verdict

Severity: Low Impact class: logic Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: Guard tmp==0 before fls(tmp) to prevent underflow

Fix applied and validated in batch kernel build (rc=0, -Werror).

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): smu7_force_clock_level computes fls(0)-1=0xFFFFFFFF when mask=0 against specific subfield; sends bogus PCIe force level. Logic bug.

Verified recommended fix

REPRODUCED (source-only): smu7_force_clock_level computes fls(0)-1=0xFFFFFFFF when mask=0 against specific subfield; sends bogus PCIe force level. Logic bug.

Verdict

REPRODUCED (source-only): smu7_force_clock_level computes fls(0)-1=0xFFFFFFFF when mask=0 against specific subfield; sends bogus PCIe force level. Logic bug.