Re: BUG #17774: Assert triggered on brin_minmax_multi.c

> On Sat, Feb 11, 2023 at 08:00:37PM +0100, Dmitry Dolgov wrote:
> > On Thu, Feb 09, 2023 at 05:18:47PM +0100, Tomas Vondra wrote:
> >
> > I believe the bug is pretty trivial - the code applies the netmask
> > incorrectly, so that with 127.0.0.1/0 it ends with 0.0.0.1, and because
> > it assumes 0.0.0.1 < 0.0.0.0 it ends with negative delta.
> >
> > In particular, the issue is that the code does this:
> >
> > lena = ip_bits(ipa); -- 0
> > len = ip_addrsize(ipa); -- 4
> >
> > for (for (i = 0; i < len; i++)
> > {
> > nbits = lena - (i * 8);
> > ...
> > mask = (0xFF << (8 - nbits));
> > ...
> > }
> >
> > But for 127.0.0.1/0 we get lena=0, so for i>0 nbits gets negative, and
> > the shift is probably going to do something silly (not sure what
> > exactly, but AFAICS it's undefined behavior).
> >
> > Attached is a fixup that resolves this failure for me. I need to look a
> > bit closer if there are some other issues (e.g. with the float rounding
> > errors, etc.).
>
> Thanks, the fix looks good and solves the issue. With the patch applied
> after a quick round of testing I haven't found any failures so far,
> whether due to float arithmetic or something else.

It occurred to me this fix wasn't applied yet, right? Are there any
concerns about it?