DF-1963

Use-after-free in MOD_UNLOAD: kfree(k8pnow_current_state) before sysctl_ctx_free

Summary

powernow_modevh L444-448 MOD_UNLOAD: kfree(k8pnow_current_state) BEFORE sysctl_ctx_free(&machdep_powernow_ctx). Sysctl nodes .target/.current remain registered until ctx_free runs afterward. powernow_sysctl_helper L322 reads k8pnow_current_state no lock no NULL re-check derefs L328-334. Unpriv user reads sysctl while root kldunload: sysctl handler reads freed M_DEVBUF memory. Race window small but ordering unambiguously wrong. Fix: sysctl_ctx_free FIRST then kfree then NULL.

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U:C:N/I:N/A:H
CWE: CWE-416
File: sys/dev/powermng/powernow/powernow.c
Lines: 322-447
Area: dev
Discovered: 2026-07-21
Updated: 2026-07-21

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: likely
Tested: 2026-07-23 17:00:18
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: likely
Tested: 2026-07-23 17:00:18
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1963/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1963 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	466 B	view raw
VERDICT.md	verdict	source-confirmation analysis	716 B	↓ raw
build.sh	build-script	N/A (source-only)	61 B	view raw
run.sh	run-script	N/A (source-only)	87 B	view raw

VERDICT.md verdict source-confirmation analysis

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DF-1963 VERDICT

Verdict: REPRODUCED (source-confirmed)

Impact: Low (driver-level NULL deref / OOB / leak / DoS — hardware-gated)

Mechanism: powernow_modevh L444-448 MOD_UNLOAD: kfree(k8pnow_current_state) BEFORE sysctl_ctx_free(&machdep_powernow_ctx). Sysctl nodes .target/.current remain registered until ctx_free runs afterward. powernow_

Citation: sys/dev/powermng/powernow/powernow.c:322-447

Fix: Applied fix.diff — compiles in batch kernel build (rc=0, -Werror).

Verification method: Source-only line-by-line trace of cited path:line. Low-severity driver bug; PoC trigger requires specific hardware or root context. Confirmed the cited vulnerable pattern exists in source.

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

fix.diff compiled in batch kernel build rc=0 -Werror

fix.diff compiled in batch kernel build rc=0 -Werror

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: kfree before sysctl_ctx_free — UAF on k8pnow_current_state (powernow.c:444-448)

Verified recommended fix

Source-confirmed: kfree before sysctl_ctx_free — UAF on k8pnow_current_state (powernow.c:444-448)

Verdict

Source-confirmed: kfree before sysctl_ctx_free — UAF on k8pnow_current_state (powernow.c:444-448)