Re: Avoid leaking system path from pg_available_extensions

Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> 于2026年5月20日周三 09:08写道：

>
>
> > 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/
>
>
>
>
> Thanks for the patch. I just reproduced the problem and verified the fix.
So this patch looks good to me.

Regards,
Lu Feng