From: Nikolay Shaplov <dhyan@nataraj.su>
To: Daniel Gustafsson <daniel@yesql.se>, pgsql-hackers@lists.postgresql.org
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>,
 egori@altlinux.org, nickel@altlinux.org, kuznetsovam@altlinux.org
Subject: Re: [PATCH] Check for TupleTableSlot nullness before dereferencing
Date: Tue, 22 Apr 2025 10:45:15 +0300
Message-ID: <2539287.KokGdZ0ToA@thinkpad-pgpro>
Organization: Postgres Professional
In-Reply-To: <18bda8da-1ab0-4a4d-9aca-826610a244a8@altlinux.org>
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From: Nikolay Shaplov <dhyan@nataraj.su>
Date: Tue, 22 Apr 2025 10:45:15 +0300
Message-ID: <2539287.KokGdZ0ToA@thinkpad-pgpro>
Organization: Postgres Professional
In-Reply-To: <18bda8da-1ab0-4a4d-9aca-826610a244a8@altlinux.org>
MIME-Version: 1.0

=D0=92 =D0=BF=D0=B8=D1=81=D1=8C=D0=BC=D0=B5 =D0=BE=D1=82 =D0=BF=D1=8F=D1=82=
=D0=BD=D0=B8=D1=86=D0=B0, 13 =D0=B4=D0=B5=D0=BA=D0=B0=D0=B1=D1=80=D1=8F 202=
4 =D0=B3. 11:54:35 MSK =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=
=82=D0=B5=D0=BB=D1=8C Alexander=20
Kuznetsov =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:
> Hello,
>=20
> ping. What do you think about reasoning below? Maybe we should consider
> proposing different patch for removing redundant check there?

Hi!

Please, pay attention that commitfest entry for this patch
https://commitfest.postgresql.org/patch/5662/
reports problems with windows build.

There is a small chance that this is flase alarm, sometimes checkers fails =
for=20
their own reason. But most probably this is persistent error, and if it is,=
=20
this problem should be researched first of all, and fixed. Only after that =
there=20
there can be any discussion if this null-related problem should be fixed or=
=20
not.


>=20
> 09.10.2024 18:23, Alexander Kuznetsov wrote:
> > 03.10.2024 12:48, Daniel Gustafsson wrote:
> >>  From a quick reading we can only reach there after evaluating an
> >> expression, so can it really be null though?  This code hasn't changed
> >> all that much since 2009, if there was a reachable segfault on a null
> >> pointer deref I have a feeling we'd heard about it by now so some extra
> >> care seems warranted to ensure it's not a static analyzer false
> >> positive.
> >=20
> > Thanks for your response!
> > It seems to me that dereferencing is possible under the following
> > scenario:
> > [...]
> > This entire reasoning is based on the assumption that slot2 can
> > theoretically be NULL, as there is such a check at line 968. Is it
> > possible that no errors have occurred because this condition has always
> > been satisfied and is, perhaps, redundant, or maybe I'm misunderstanding
> > something?


=2D-=20
Nikolay Shaplov aka Nataraj
=46uzzing Engineer at Postgres Professional
Matrix IM: @dhyan:nataraj.su

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