Re: BUG #17280: global-buffer-overflow on select from pg_stat_slru

At Thu, 11 Nov 2021 17:08:34 +0900, Michael Paquier <michael(at)paquier(dot)xyz> wrote in
> On Thu, Nov 11, 2021 at 12:19:09PM +0900, Kyotaro Horiguchi wrote:
> > I'm not sure which is easier to read, but it might be a bit hard since
> > the conditino term in not mention counter itself. I don't object to
> > that way. And, yes SLRU_NUM_ELEMENTS cannot be used here:p
> >
> > The attached is the first way in the choices.
>
> That looks fine.
>
> Also, what do you think about adding a test in sysviews.sql? This
> could be as simple as that:
> SELECT count(*) > 0 AS ok FROM pg_stat_slru;

Rahter it is touching only pg_stat_wal and pg_stat_walreceiver among
42 pg_stat_* views. However I agree to it is good to add it for the
reason mentioned below.

> I am not sure if the buildfarm animals running valgrind would have
> caught this issue, but having something would be better than nothing
> for this case.

Valgrind didn't detect that for me (-O0). The address area accessed
by the overun is allocated to other variables. That being said. I
agree that causing access to the full range of the variable should
help checker tools. And that ends in a time shorter than a blink.

Please find the attached.

regrds.

--
Kyotaro Horiguchi
NTT Open Source Software Center