Summary

SYSCTL_ADD_PROC L250-256 flags include CTLFLAG_ANYBODY for all 5 HCI sysctls (force_fan/video_output/lcd_brightness/lcd_backlight/cpu_speed). kern_sysctl.c:1446 CTLFLAG_ANYBODY bypasses caps_priv_check(SYSCAP_NOSYSCTL_WR). Any local unpriv user sysctlbyname hw.acpi.toshiba.{cpu_speed,lcd_backlight,force_fan,...} succeeds. hci_cpu_speed accepts 0..7 full CPU throttle range L392-407; hci_lcd_backlight value 0 blanks panel for all VTs/users L380-390. Shared/lab host local DoS affecting all users. No memory corruption/escalation. Pattern consistent with sibling drivers acpi_fujitsu/acpi_panasonic/acpi_asus. Fix: drop CTLFLAG_ANYBODY enforce SYSCAP_NOSYSCTL_WR root-or-cap.

PoC verification

Evidence pack

findings/poc/DF-1892 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	470 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-1892 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: SYSCTL_ADD_PROC L250-256 flags include CTLFLAG_ANYBODY for all 5 HCI sysctls (force_fan/video_output/lcd_brightness/lcd_backlight/cpu_speed). kern_sysctl.c:1446 CTLFLAG_ANYBODY bypasses caps_priv_chec

Citation: sys/dev/acpica/acpi_toshiba/acpi_toshiba.c:250-256

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: CTLFLAG_ANYBODY bypasses SYSCAP_NOSYSCTL_WR on HCI sysctls (acpi_toshiba.c:250-256)

Verified recommended fix

Source-confirmed: CTLFLAG_ANYBODY bypasses SYSCAP_NOSYSCTL_WR on HCI sysctls (acpi_toshiba.c:250-256)

Verdict