From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 25 Jun 2025 01:03:54 +0000 (+0900)
Subject: Avoid scribbling of VACUUM options
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=refs%2Fheads%2FREL_14_STABLE;p=postgresql.git

Avoid scribbling of VACUUM options

This fixes two issues with the handling of VacuumParams in vacuum_rel().
This code path has the idea to change the passed-in pointer of
VacuumParams for the "truncate" and "index_cleanup" options for the
relation worked on, impacting the two following scenarios where
incorrect options may be used because a VacuumParams pointer is shared
across multiple relations:
- Multiple relations in a single VACUUM command.
- TOAST relations vacuumed with their main relation.

The problem is avoided by providing to the two callers of vacuum_rel()
copies of VacuumParams, before the pointer is updated for the "truncate"
and "index_cleanup" options.

The refactoring of the VACUUM option and parameters done in 0d831389749a
did not introduce an issue, but it has encouraged the problem we are
dealing with in this commit, with b84dbc8eb80b for "truncate" and
a96c41feec6b for "index_cleanup" that have been added a couple of years
after the initial refactoring.  HEAD will be improved with a different
patch that hardens the uses of VacuumParams across the tree.  This
cannot be backpatched as it introduces an ABI breakage.

The backend portion of the patch has been authored by Nathan, while I
have implemented the tests.  The tests rely on injection points to check
the option values, making them faster, more reliable than the tests
originally proposed by Shihao, and they also provide more coverage.
This part can only be backpatched down to v17.

Reported-by: Shihao Zhong <zhong950419@gmail.com>
Author: Nathan Bossart <nathandbossart@gmail.com>
Co-authored-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CAGRkXqTo+aK=GTy5pSc-9cy8H2F2TJvcrZ-zXEiNJj93np1UUw@mail.gmail.com
Backpatch-through: 13
---

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index da06234fdc9..1c9b3d1a8f7 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -473,7 +473,14 @@ vacuum(List *relations, VacuumParams *params,
 
 			if (params->options & VACOPT_VACUUM)
 			{
-				if (!vacuum_rel(vrel->oid, vrel->relation, params))
+				VacuumParams params_copy;
+
+				/*
+				 * vacuum_rel() scribbles on the parameters, so give it a copy
+				 * to avoid affecting other relations.
+				 */
+				memcpy(&params_copy, params, sizeof(VacuumParams));
+				if (!vacuum_rel(vrel->oid, vrel->relation, &params_copy))
 					continue;
 			}
 
@@ -1839,9 +1846,16 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params)
 	Oid			save_userid;
 	int			save_sec_context;
 	int			save_nestlevel;
+	VacuumParams toast_vacuum_params;
 
 	Assert(params != NULL);
 
+	/*
+	 * This function scribbles on the parameters, so make a copy early to
+	 * avoid affecting the TOAST table (if we do end up recursing to it).
+	 */
+	memcpy(&toast_vacuum_params, params, sizeof(VacuumParams));
+
 	/* Begin a transaction for vacuuming this relation */
 	StartTransactionCommand();
 
@@ -2092,7 +2106,7 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params)
 	 * totally unimportant for toast relations.
 	 */
 	if (toast_relid != InvalidOid)
-		vacuum_rel(toast_relid, NULL, params);
+		vacuum_rel(toast_relid, NULL, &toast_vacuum_params);
 
 	/*
 	 * Now release the session-level lock on the main table.