Signed-integer overflow in callout timer calc (min_period*hz/2) -> self-perpetuating CPU-burn or watchdog defeat

Summary

wdog_reset_all(:105) min_period*hz/2 in int. min_period from INT_MAX init or driver return. >INT_MAX/hz -> signed overflow -> negative/wrong ticks. callout fires immediately -> CPU-burn (self-re-scheduling callback) or fails to arm -> hardware reset. Root via sysctl or driver bug.