Re: Avoid leaking system path from pg_available_extensions

> On May 20, 2026, at 09:00, Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>
> Hi,
>
> I just tested “Add paths of extensions to pg_available_extensions”, and found an issue.
>
> This is a simple repro:
> ```
> evantest=# reset extension_control_path;
> RESET
> evantest=# select * from pg_available_extensions where name = 'plpgsql';
> name | default_version | installed_version | location | comment
> ---------+-----------------+-------------------+----------+------------------------------
> plpgsql | 1.0 | 1.0 | $system | PL/pgSQL procedural language
> (1 row)
>
> evantest=# set extension_control_path='';
> SET
> evantest=# select * from pg_available_extensions where name = 'plpgsql';
> name | default_version | installed_version | location | comment
> ---------+-----------------+-------------------+----------------------------------+------------------------------
> plpgsql | 1.0 | 1.0 | /usr/local/pgsql/share/extension | PL/pgSQL procedural language
> (1 row)
> ```
>
> When extension_control_path is not set, location shows “$system", which is consistent with what the documentation says:
> ```
> <para>
> The default value for this parameter is
> <literal>'$system'</literal>. If the value is set to an empty
> string, the default <literal>'$system'</literal> is also assumed.
> </para>
> ```
>
> However, as shown above, when I set extension_control_path to an empty string, the absolute system path is displayed. I consider this an information leakage bug.
>
> The fix is straightforward; see the attached patch for details. After the fix, when extension_control_path is an empty string, location shows “$system” now:
> ```
> evantest=# set extension_control_path='';
> SET
> evantest=# select * from pg_available_extensions where name = 'plpgsql';
> name | default_version | installed_version | location | comment
> ---------+-----------------+-------------------+----------+------------------------------
> plpgsql | 1.0 | 1.0 | $system | PL/pgSQL procedural language
> (1 row)
> ```
>
> Best regards,
> --
> Chao Li (Evan)
> HighGo Software Co., Ltd.
> https://www.highgo.com/
>
>
>
>

Oops, forgot the attachment. Here comes it.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/