Re: [libgpiod] Integer overflow in C++ binding on 32bit systems causes wrong event timestamps

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Sun, Sep 6, 2020 at 6:52 PM Florian Evers <florian-evers@xxxxxx> wrote:
>
> Hello,
>
> I found a bug in the c++ bindings of libgpiod that affects 32bit systems.
>
> Observation:
>
> Only the c++ bindings lib is affected. For input events, the time stamp
> delivered in the event object is wrong. Instead of providing a complete
> "system time", it delivers time stamps of of a range "-2.1"...+2.1 seconds
> (which relates to the time stamp range of a signed 32bit value, in
> nanoseconds).
>
> Cause:
>
> The bug is in line 219 of file "/tree/bindings/cxx/line.cpp":
>
> event.ts.tv_nsec + (event.ts.tv_sec * 1000000000));
>
> "event.ts.tv_sec" is of type signed long, which is 32 bit on my device. Thus,
> that multiplication to convert total seconds of a system time to nanoseconds
> causes an overflow.
>
> Fix:
>
> There should be a cast to uint64_t before the multiplication.
>
> Thank you for fixing this!
>
> Regards,
> Florian

Hi Florian,

thanks for the report! I see Kent already sent a fix - could you test
it on your setup?

Thanks in advance,
Bartosz Golaszewski