# DF-2392 VERDICT

**Status:** reproduced (reproduced)
**Impact:** panic
**Confidence:** certain
**Attempts:** 1

STOCK kernel (X86_64_GENERIC #0): sysctl -w machdep.acpi_timer_freq=0 is accepted by acpi_timer_sysctl_freq (only the CURRENT frequency is validated at acpi_timer.c:310-311) and forwarded unchanged to cputimer_set_frequency, which divides by it - Fatal trap 18 integer divide fault, Stopped at cputimer_set_frequency+0x10 (divq %rsi,%eax), guest dies. Single privileged sysctl write, deterministic, no special hardware state. Fixed kernel rejects the write with EINVAL (Invalid argument).

## Kernel references
- `sys/dev/acpica/acpi_timer.c:307`
- `sys/dev/acpica/acpi_timer.c:316`
- `sys/kern/kern_cputimer.c:190`

## Guest
DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026     root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64

## Fix validation
See fix.diff and README.md for the baseline/fixed A/B outputs (run.log / fixed.log).

## 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.