Date: Sun, 30 Nov 2025 10:27:12 +0900 (JST)
Message-Id: <20251130.102712.131456481338876013.ishii@postgresql.org>
To: zam6ak@gmail.com
Cc: pgpool-general@lists.postgresql.org
Subject: Re: "buffer overflow detected" when running SHOW POOL_STATUS
From: Tatsuo Ishii <ishii@postgresql.org>
In-Reply-To: 
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Hello,

Thank you for the report!

Unfortunately, I was not able to reproduce the issue on my Ubuntu 24
and Rocky Linux 10.1 box (pgpool is compiled from source code).
So there are some questions:

- Is the issue occurred even when you execute other pgpool command?
  (for example "show pool_processes")

- I found a problem with the output of "show pool_status". The value
  of "memqcache_stats_start_time" is shown with newline and an empty
  item followed. I am not sure if this is related to your issue. If
  possible, can you please try the attached patch?

Best regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp

> Hello
> 
> I am using the latest pgpool-II v4.6.4 on Rocky Linux v10.1
> (installation via RPMs) with PostgreSQL 18 (one primary, one replica,
> streaming replication)
> When attempting to run POOL_STATUS command, either as SQL or via pcp,
> I am getting "buffer overflow detected" in the log.
> Here are the contents of the log from both SQL and pcp commands:
> 
> 1)
> sudo -u postgres pcp_pool_status -w -v -h localhost -p 9898 -U postgres
> 
> 2025-11-27 13:30:19.298 [4486]: [3-1] user=[No Connection],db=[No
> Connection],app=pcp_main LOG:  forked new pcp worker, pid=4495
> socket=7
> 2025-11-27 13:30:19.298 [4486]: [4-1] user=[No Connection],db=[No
> Connection],app=pcp_main LOCATION:  pcp_child.c:327
> *** buffer overflow detected ***: terminated
> 2025-11-27 13:30:20.315 [4486]: [5-1] user=[No Connection],db=[No
> Connection],app=pcp_main LOG:  PCP process with pid: 4495 exits with
> status 134 by signal 6
> 2025-11-27 13:30:20.315 [4486]: [6-1] user=[No Connection],db=[No
> Connection],app=pcp_main LOCATION:  pcp_child.c:394
> 
> 2)
> sudo -u postgres psql -w -h localhost -p 9999 -U postgres -c "SHOW POOL_STATUS"
> 
> 2025-11-27 13:31:34.385 [4390]: [1-1]
> user=postgres,db=postgres,app=psql LOG:  DB node id: 0 backend pid:
> 10166 statement: SELECT pg_catalog.version()
> 2025-11-27 13:31:34.385 [4390]: [2-1]
> user=postgres,db=postgres,app=psql LOCATION:
> pool_proto_modules.c:3803
> *** buffer overflow detected ***: terminated
> 
> 
> 
> And here is my pgpool.conf file (only changed lines - diff compared to
> pgpool.conf.sample)
> diff --unchanged-line-format= --old-line-format=
> --new-line-format='%L' pgpool.conf.sample pgpool.conf
> 
> listen_addresses = '*'
> unix_socket_directories = '/var/run/pgpool'
> pcp_socket_dir = '/var/run/pgpool'
> serialize_accept = on
> backend_hostname0 = '192.168.68.104'
> backend_port0 = 5432
> backend_weight0 = 1
> backend_data_directory0 = '/data/pgdata/18'
> backend_flag0 = 'ALWAYS_PRIMARY'
> backend_application_name0 = 'primary'
> backend_hostname1 = '192.168.68.105'
> backend_port1 = 5432
> backend_weight1 = 1
> backend_data_directory1 = '/data/pgdata/18'
> backend_flag1 = 'DISALLOW_TO_FAILOVER'
> backend_application_name1 = 'replica_1'
> num_init_children = 96
> max_pool = 2
> child_life_time = 0
> log_line_prefix = '%m [%p]: [%l-1] user=%u,db=%d,app=%a '   #
> printf-style string to output at beginning of each log line.
> log_connections = off
> log_disconnections = off
> log_per_node_statement = on
> log_standby_delay = 'always'
> log_error_verbosity = verbose          # terse, default, or verbose messages
> log_filename = 'pgpool-01-%a.log'
> write_function_list =
> 'currval,lastval,nextval,setval,public.upgrade_.*,upgrade_.*,public.update_.*,update_.*,public.selsert_.*,selsert_.*,public.purge_.*,purge_.*,public.process_.*,process_.*,public.move_.*,move_.*,public.merge_.*,merge_.*,public.mark_.*,mark_.*,billing.can_ahs_claim_charge,billing.can_ahs_apply_.*'
> statement_level_load_balance = on
> sr_check_period = 5s
> sr_check_user = 'pgpool_monitor'
> delay_threshold_by_time = 500ms
> health_check_period = 10
> health_check_timeout = 30
> health_check_user = 'pgpool_monitor'
> health_check_max_retries = 10
> failover_on_backend_error = off
> check_temp_table = trace
> 
> 

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diff --git a/src/utils/pool_process_reporting.c b/src/utils/pool_process_reporting.c
index e4fcf4457..9e677d95e 100644
--- a/src/utils/pool_process_reporting.c
+++ b/src/utils/pool_process_reporting.c
@@ -1117,6 +1117,8 @@ get_config(int *nrows)
 
 	StrNCpy(status[i].name, "memqcache_stats_start_time", POOLCONFIG_MAXNAMELEN);
 	snprintf(status[i].value, POOLCONFIG_MAXVALLEN, "%s", ctime(&pool_get_memqcache_stats()->start_time));
+	/* remove a newline added by ctime() */
+	*(strchrnul(status[i].value, '\n')) = '\0';
 	StrNCpy(status[i].desc, "Start time of query cache stats", POOLCONFIG_MAXDESCLEN);
 	i++;
 

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