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From: Nikolay Shaplov <[email protected]>
To: Daniel Gustafsson <[email protected]>
To: [email protected]
Cc: PostgreSQL Developers <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Subject: Re: [PATCH] Check for TupleTableSlot nullness before dereferencing
Date: Tue, 22 Apr 2025 10:45:15 +0300
Message-ID: <2539287.KokGdZ0ToA@thinkpad-pgpro> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>

В письме от пятница, 13 декабря 2024 г. 11:54:35 MSK пользователь Alexander 
Kuznetsov написал:
> Hello,
> 
> 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 
their own reason. But most probably this is persistent error, and if it is, 
this problem should be researched first of all, and fixed. Only after that there 
there can be any discussion if this null-related problem should be fixed or 
not.


> 
> 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.
> > 
> > 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?


-- 
Nikolay Shaplov aka Nataraj
Fuzzing Engineer at Postgres Professional
Matrix IM: @dhyan:nataraj.su


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