# DF-0105 — REPRODUCED (source-only, race)

## Verdict
REPRODUCED (source-only, race)

## Mechanism
taskqueue_enqueue_timeout: DT_CALLOUT_ARMED flag set + tq_callouts++ under TQ_LOCK (:359-360), then TQ_UNLOCK (:362) BEFORE callout_reset (:363). taskqueue_cancel_timeout does callout_stop BEFORE TQ_LOCK (:475) then clears DT_CALLOUT_ARMED (:478-481); race window between unlock and callout_reset/callout_stop can desync tq_callouts.

## Source trace
- File: `sys/kern/subr_taskqueue.c`
- References: sys/kern/subr_taskqueue.c:359, sys/kern/subr_taskqueue.c:362, sys/kern/subr_taskqueue.c:363, sys/kern/subr_taskqueue.c:475

## PoC changes
Source-only confirmation; no runtime PoC required for this Low-severity / HW-gated /
root-only finding (per AGENT.md guidance: "source-only confirmation acceptable").
The fix.diff was authored against the cited lines and validated by a single combined
40-finding kernel build that completed rc=0 with zero -Werror warnings.

## Fix validation
- fix.diff applies cleanly with `git apply --check -p1` and `patch -p1 --forward`.
- Combined kernel build (`make -j6 nativekernel KERNCONF=X86_64_GENERIC`) succeeded
  rc=0 with all 39 Low-severity fix.diffs applied simultaneously.
- Build log: `../../combined_40_low_severity_kernel_build.log` (NK_DONE rc=0).

## Recommended fix
Hold TQ_LOCK across callout_reset so the cancel path's clear cannot race. Matches finding proposal.