Re: Fix possible dereference null pointer (src/backend/replication/logical/reorderbuffer.c) - Mailing list pgsql-hackers

From Ranier Vilela
Subject Re: Fix possible dereference null pointer (src/backend/replication/logical/reorderbuffer.c)
Date
Msg-id CAEudQAop7_XOPXwAozbyyugHw+Ca5Lur5hRo3SrusRLwV7n8Ng@mail.gmail.com
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In response to Re: Fix possible dereference null pointer (src/backend/replication/logical/reorderbuffer.c)  (Heikki Linnakangas <hlinnaka@iki.fi>)
Responses Re: Fix possible dereference null pointer (src/backend/replication/logical/reorderbuffer.c)
List pgsql-hackers
Em qui., 11 de abr. de 2024 às 09:54, Heikki Linnakangas <hlinnaka@iki.fi> escreveu:
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.
Thanks for the clarification.
I will then suggest improving robustness, 
but avoiding hiding any possible errors that may occur.

v1 patch attached.

best regards,
Ranier Vilela
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