BUG #17326: Postgres crashed when pg_reload_conf() with ssl certificate parameters

The following bug has been logged on the website:

Bug reference:      17326
Logged by:          James Pang
Email address:      chaolpan@cisco.com
PostgreSQL version: 13.4
Operating system:   RHEL8.4
Description:

we need SSL enabled for our production env, when I test renew a ssl
certificate , and reload_conf, it crashed. even with same certificate and
ssl parameters, run reload_conf often lead to Postgres crash. For example
:

 =# select name,setting from pg_settings where name like 'ssl_%' order by
name;
                  name                  |                setting
----------------------------------------+---------------------------------------
 ssl_ca_file                            |
/var/lib/pgsql/sslcerts/awstestca.crt
 ssl_cert_file                          |
/var/lib/pgsql/sslcerts/server.crt
 ssl_ciphers                            | HIGH:MEDIUM:+3DES:!aNULL
 ssl_crl_file                           |
 ssl_dh_params_file                     |
 ssl_ecdh_curve                         | prime256v1
 ssl_key_file                           |
/var/lib/pgsql/sslcerts/server.key
 ssl_library                            | OpenSSL
 ssl_max_protocol_version               |
 ssl_min_protocol_version               | TLSv1.2
 ssl_passphrase_command                 |
 ssl_passphrase_command_supports_reload | off
 ssl_prefer_server_ciphers              | on
(13 rows)

 =# select pg_reload_conf();
 pg_reload_conf
----------------
 t
(1 row)

 =# select pg_reload_conf();
 pg_reload_conf
----------------
 t
(1 row)

 =# select pg_reload_conf();
FATAL:  terminating connection due to unexpected postmaster exit
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.