On Sat, Oct 07, 2023 at 07:58:57PM +0900, FUJITA Tomonori wrote:

quoted

Since we're taking user input, it probably doesn't hurt to do some
sort of sanity check rather than casting. Maybe warn once then return
the biggest nowrapping value

    let speed_i32 = i32::try_from(speed).unwrap_or_else(|_| {
        warn_once!("excessive speed {speed}");

NEVER call WARN() on user input, as you now just rebooted the machine
and caused a DoS (and syzbot will start to spam you with reports.)

Remember, the majority of Linux systems in the world run with
panic-on-warn enabled, so any user path that can cause this, will be
used to cause problems.

thanks,

greg k-h