> It's becouse 3.3 already contains some fixes which was not be backported
> to older versions.

Yes, exactly!  That's what I meant when I said:

"So far, I've been fixing these overflow bugs only in the development branches"

There were lots of integer overflow occurrences like these found by John Regehr in issue 9530.  I chose to fix those only in the current development branch, which was 3.3 at the time.  Since we've made an effort to clean up 3.3 in that respect, I think it's worth finishing that job off by applying your patch both to 3.3 and 3.4.