public inbox for [email protected]
help / color / mirror / Atom feedFrom: Tom Lane <[email protected]>
To: [email protected]
Subject: pgsql: Remove race condition in pg_get_expr().
Date: Fri, 09 Feb 2024 17:29:54 +0000
Message-ID: <[email protected]> (raw)
Remove race condition in pg_get_expr().
Since its introduction, pg_get_expr() has intended to silently
return NULL if called with an invalid relation OID, as can happen
when scanning the catalogs concurrently with relation drops.
However, there is a race condition: we check validity of the OID
at the start, but it could get dropped just afterward, leading to
failures. This is the cause of some intermittent instability we're
seeing in a proposed new test case, and presumably it's a hazard in
the field as well.
We can fix this by AccessShareLock-ing the target relation for the
duration of pg_get_expr(). Since we don't require any permissions
on the target relation, this is semantically a bit undesirable. But
it turns out that the set_relation_column_names() subroutine already
takes a transient AccessShareLock on that relation, and has done since
commit 2ffa740be in 2012. Given the lack of complaints about that, it
seems like there should be no harm in holding the lock a bit longer.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/[email protected]
Branch
------
REL_13_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/ceb224b62b9d66bdf8584b01c103268d3b90d577
Modified Files
--------------
src/backend/utils/adt/ruleutils.c | 68 +++++++++++++++++++--------------------
1 file changed, 33 insertions(+), 35 deletions(-)
view thread (6+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected]
Subject: Re: pgsql: Remove race condition in pg_get_expr().
In-Reply-To: <[email protected]>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox