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.

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	1.0 KB	↓ raw
build.sh	build-script	N/A (source-only)	65 B	view raw
run.sh	run-script	N/A (source-only)	89 B	view raw

VERDICT.md verdict source-confirmation analysis

↓ download raw

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 status (batch validation)

Applied with the 36 sibling fix.diffs of this batch in findings/poc/_batch41/all_fixes.patch; single in-guest make -j6 nativekernel KERNCONF=X86_64_GENERIC completed RC=0 with zero errors under -Werror (full log: findings/poc/_batch41/fix_build8.log). Behavior A/B intentionally skipped for this Info-tier item.

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