Message-ID: <5967fcdc-0211-4549-8ade-03d21ccf7566@iki.fi>
Date: Thu, 11 Apr 2024 15:54:33 +0300
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Subject: Re: Fix possible dereference null pointer
 (src/backend/replication/logical/reorderbuffer.c)
To: Ranier Vilela <ranier.vf@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
References: <CAEudQApm0Kffq4GKLdyogyW1tVbkHOOqWTWg169OTsm1W=FUHg@mail.gmail.com>
 <02c62e7e-df6b-4b50-8b9e-cdcb3b45c74e@iki.fi>
 <CAEudQAp9auHMmBf-jS_-eaE+hQ6dNRJuBJmkGzrMtKndnOCQ9Q@mail.gmail.com>
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From: Heikki Linnakangas <hlinnaka@iki.fi>
In-Reply-To: <CAEudQAp9auHMmBf-jS_-eaE+hQ6dNRJuBJmkGzrMtKndnOCQ9Q@mail.gmail.com>
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On 11/04/2024 15:03, Ranier Vilela wrote:
> Em qua., 10 de abr. de 2024 às 18:28, Heikki Linnakangas 
> <hlinnaka@iki.fi <mailto:hlinnaka@iki.fi>> escreveu:
> 
>     On 10/04/2024 21:07, Ranier Vilela wrote:
>      > Hi,
>      >
>      > Per Coverity.
>      >
>      > The function ReorderBufferTXNByXid,
>      > can return NULL when the parameter *create* is false.
>      >
>      > In the functions ReorderBufferSetBaseSnapshot
>      > and ReorderBufferXidHasBaseSnapshot,
>      > the second call to ReorderBufferTXNByXid,
>      > pass false to *create* argument.
>      >
>      > In the function ReorderBufferSetBaseSnapshot,
>      > fixed passing true as argument to always return
>      > a valid ReorderBufferTXN pointer.
>      >
>      > In the function ReorderBufferXidHasBaseSnapshot,
>      > fixed by checking if the pointer is NULL.
> 
>     If it's a "known subxid", the top-level XID should already have its
>     ReorderBufferTXN entry, so ReorderBufferTXN() should never return NULL.
> 
> There are several conditions to not return NULL,
> I think trusting never is insecure.

Well, you could make it an elog(ERROR, ..) instead. But the point is 
that it should not happen, and if it does for some reason, that's very 
suprpising and there is a bug somewhere. In that case, we should *not* 
just blindly create it and proceed as if everything was OK.

-- 
Heikki Linnakangas
Neon (https://neon.tech)