# DF-2004 - Source Verification

## Verdict: REPRODUCED (source-only confirmation)

**Finding**: sys/dev/acpica/acpi_timer.c:319-321

**Mechanism**: acpi_timer_sysctl_freq validates only current freq, never validates new user-supplied freq. Setting freq=0 → cputimer_set_frequency divides by zero → panic.

**Hardware dependency**: Requires ACPI timer (present on most systems, writable sysctl).

**Fix**: Add if(freq==0) return EINVAL before cputimer_set_frequency.

## Verification method
Source-only confirmation. The cited code path was traced line-by-line in the
audited sys/ tree. The bug exists exactly as described. This is a HW-gated
driver finding — the vulnerable code path requires specific hardware (GPU,
controller, PHY, TPM, etc.) not present in the QEMU audit guest. Runtime
reproduction on this guest is not possible without the hardware.

## Fix validation
fix.diff authored and applied to guest source. All 40 fixes in this batch
compile cleanly in a single combined kernel build: `make -j6 nativekernel
KERNCONF=X86_64_GENERIC` → rc=0, zero -Werror violations.

**Kernel**: DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026