From 8e2b6d45a033287da7c8f63062129ea02d86d831 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 2 Feb 2022 13:50:33 -0500
Subject: [PATCH] Fix server crash bug in 'server' backup target.
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When this code executed as superuser it appeared to work because no
system catalog lookups happened, but otherwise it crashes because there
is no transaction environment. Fix that.

Report and code change by me. Test case by Dagfinn Ilmari Mannsåker.

Discussion: http://postgr.es/m/CA+TgmobiKLXne-2AVzYyWRiO8=rChBQ=7ywoxp=2SmcFw=oDDw@mail.gmail.com
---
 src/backend/replication/basebackup_server.c  |  3 +++
 src/bin/pg_basebackup/t/010_pg_basebackup.pl | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/backend/replication/basebackup_server.c b/src/backend/replication/basebackup_server.c
index 18b0e11d903..a8786296686 100644
--- a/src/backend/replication/basebackup_server.c
+++ b/src/backend/replication/basebackup_server.c
@@ -10,6 +10,7 @@
  */
 #include "postgres.h"
 
+#include "access/xact.h"
 #include "catalog/pg_authid.h"
 #include "miscadmin.h"
 #include "replication/basebackup.h"
@@ -67,10 +68,12 @@ bbsink_server_new(bbsink *next, char *pathname)
 	sink->base.bbs_next = next;
 
 	/* Replication permission is not sufficient in this case. */
+	StartTransactionCommand();
 	if (!is_member_of_role(GetUserId(), ROLE_PG_WRITE_SERVER_FILES))
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("must be superuser or a member of the pg_write_server_files role to create server backup")));
+	CommitTransactionCommand();
 
 	/*
 	 * It's not a good idea to store your backups in the same directory that
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index a827be5e592..2283a8c42d5 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -10,7 +10,7 @@ use File::Path qw(rmtree);
 use Fcntl qw(:seek);
 use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
-use Test::More tests => 143;
+use Test::More;
 
 program_help_ok('pg_basebackup');
 program_version_ok('pg_basebackup');
@@ -521,6 +521,15 @@ $node->command_ok(
 ok(-f "$tempdir/backuponserver/base.tar", 'backup tar was created');
 rmtree("$tempdir/backuponserver");
 
+$node->command_ok(
+	[qw(createuser --replication --role=pg_write_server_files backupuser)],
+	'create backup user');
+$node->command_ok(
+	[ @pg_basebackup_defs, '-U', 'backupuser', '--target', "server:$real_tempdir/backuponserver", '-X', 'none' ],
+	'backup target server');
+ok(-f "$tempdir/backuponserver/base.tar", 'backup tar was created as non-superuser');
+rmtree("$tempdir/backuponserver");
+
 $node->command_fails(
 	[
 		@pg_basebackup_defs,         '-D',
@@ -768,3 +777,5 @@ SKIP:
 	rmtree("$tempdir/backup_gzip2");
 	rmtree("$tempdir/backup_gzip3");
 }
+
+done_testing();