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From: Andres Freund <[email protected]>
To: Fabien COELHO <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: psql - add SHOW_ALL_RESULTS option
Date: Wed, 12 Jan 2022 21:44:33 -0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2201081931170.731324@pseudo>
References: <[email protected]>
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	<[email protected]>
	<alpine.DEB.2.22.394.2109251058000.3216312@pseudo>
	<alpine.DEB.2.22.394.2110021622530.2817726@pseudo>
	<[email protected]>
	<alpine.DEB.2.22.394.2112230703530.2668598@pseudo>
	<[email protected]>
	<alpine.DEB.2.22.394.2201040851220.3857182@pseudo>
	<alpine.DEB.2.22.394.2201081931170.731324@pseudo>

Hi,

On 2022-01-08 19:32:36 +0100, Fabien COELHO wrote:
> Attached v13 where the crash test is moved to tap.

The reason this test constantly fails on cfbot windows is a use-after-free
bug.

I figured that out in the context of another thread, so the debugging is
there:

https://postgr.es/m/20220113054123.ib4khtafgq34lv4z%40alap3.anarazel.de
> Ah, I see the bug. It's a use-after-free introduced in the patch:
>
> SendQueryAndProcessResults(const char *query, double *pelapsed_msec,
> 	bool is_watch, const printQueryOpt *opt, FILE *printQueryFout, bool *tx_ended)
> 
> 
> ...
> 	/* first result */
> 	result = PQgetResult(pset.db);
> 
> 
> 	while (result != NULL)
> 
> 
> ...
> 		if (!AcceptResult(result, false))
> 		{
> ...
> 			ClearOrSaveResult(result);
> 			success = false;
> 
> 
> 			/* and switch to next result */
> 			result_status = PQresultStatus(result);
> 			if (result_status == PGRES_COPY_BOTH ||
> 				result_status == PGRES_COPY_OUT ||
> 				result_status == PGRES_COPY_IN)
> 
> 
> So we called ClearOrSaveResult() with did a PQclear(), and then we go and call
> PQresultStatus().

Greetings,

Andres Freund

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