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Re: Assert name/short_desc to prevent SHOW ALL segfault

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Steve Chavez <steve@supabase.io>
Cc: pgsql-hackers@postgresql.org
Date: 2022-05-24T18:41:49Z
Lists: pgsql-hackers 
On Mon, May 23, 2022 at 11:39:16PM -0500, Steve Chavez wrote:
> The DefineCustomStringVariable function(or any
> other DefineCustomXXXVariable) has a short_desc parameter that can be
> NULL and it's not apparent that this will lead to a segfault when SHOW ALL
> is used.
> This happens because the ShowAllGUCConfig function expects a non-NULL
> short_desc.
> 
> This happened for the Supabase supautils extension(
> https://github.com/supabase/supautils/issues/24) and any other extension
> that uses the DefineCustomXXXVariable has the same bug risk.
> 
> This patch does an Assert on the short_desc(also on the name as an extra
> measure), so a postgres built with --enable-cassert can prevent the above
> issue.

I would actually ERROR on this so that we aren't relying on
--enable-cassert builds to catch it.  That being said, if there's no strong
reason to enforce that a short description be provided, then why not adjust
ShowAllGUCConfig() to set that column to NULL when short_desc is missing?

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Introduce pg_attribute_nonnull(...)

  2. Handle NULL for short descriptions of custom GUC variables