Check for CREATE privilege on the schema in CREATE STATISTICS.

This omission allowed table owners to create statistics in any
schema, potentially leading to unexpected naming conflicts.  For
ALTER TABLE commands that require re-creating statistics objects,
skip this check in case the user has since lost CREATE on the
schema.  The addition of a second parameter to CreateStatistics()
breaks ABI compatibility, but we are unaware of any impacted
third-party code.

Reported-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Author: Jelte Fennema-Nio <postgres@jeltef.nl>
Co-authored-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Security: CVE-2025-12817
Backpatch-through: 13

Author: nathan-bossart

src/backend/commands/statscmds.c

@@ -62,7 +62,7 @@ compare_int16(const void *a, const void *b)
  *		CREATE STATISTICS
  */
 ObjectAddress
-CreateStatistics(CreateStatsStmt *stmt)
+CreateStatistics(CreateStatsStmt *stmt, bool check_rights)
 {
 	int16		attnums[STATS_MAX_DIMENSIONS];
 	int			nattnums = 0;
@@ -175,6 +175,20 @@ CreateStatistics(CreateStatsStmt *stmt)
 	}
 	namestrcpy(&stxname, namestr);
 
+	/*
+	 * Check we have creation rights in target namespace.  Skip check if
+	 * caller doesn't want it.
+	 */
+	if (check_rights)
+	{
+		AclResult	aclresult;
+
+		aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(), ACL_CREATE);
+		if (aclresult != ACLCHECK_OK)
+			aclcheck_error(aclresult, OBJECT_SCHEMA,
+						   get_namespace_name(namespaceId));
+	}
+
 	/*
 	 * Deal with the possibility that the statistics object already exists.
 	 */

src/backend/commands/tablecmds.c

@@ -8662,7 +8662,7 @@ ATExecAddStatistics(AlteredTableInfo *tab, Relation rel,
 	/* The CreateStatsStmt has already been through transformStatsStmt */
 	Assert(stmt->transformed);
 
-	address = CreateStatistics(stmt);
+	address = CreateStatistics(stmt, !is_rebuild);
 
 	return address;
 }

src/backend/tcop/utility.c

@@ -1881,7 +1881,7 @@ ProcessUtilitySlow(ParseState *pstate,
 					/* Run parse analysis ... */
 					stmt = transformStatsStmt(relid, stmt, queryString);
 
-					address = CreateStatistics(stmt);
+					address = CreateStatistics(stmt, true);
 				}
 				break;
 

src/include/commands/defrem.h

@@ -80,7 +80,7 @@ extern void RemoveOperatorById(Oid operOid);
 extern ObjectAddress AlterOperator(AlterOperatorStmt *stmt);
 
 /* commands/statscmds.c */
-extern ObjectAddress CreateStatistics(CreateStatsStmt *stmt);
+extern ObjectAddress CreateStatistics(CreateStatsStmt *stmt, bool check_rights);
 extern ObjectAddress AlterStatistics(AlterStatsStmt *stmt);
 extern void RemoveStatisticsById(Oid statsOid);
 extern Oid	StatisticsGetRelation(Oid statId, bool missing_ok);

src/test/regress/expected/stats_ext.out

@@ -3371,6 +3371,23 @@ SELECT statistics_name, most_common_vals FROM pg_stats_ext_exprs x
  s_expr          | {1}
 (2 rows)
 
+-- CREATE STATISTICS checks for CREATE on the schema
+RESET SESSION AUTHORIZATION;
+CREATE SCHEMA sts_sch1 CREATE TABLE sts_sch1.tbl (a INT, b INT);
+GRANT USAGE ON SCHEMA sts_sch1 TO regress_stats_user1;
+ALTER TABLE sts_sch1.tbl OWNER TO regress_stats_user1;
+SET SESSION AUTHORIZATION regress_stats_user1;
+CREATE STATISTICS sts_sch1.fail ON a, b FROM sts_sch1.tbl;
+ERROR:  permission denied for schema sts_sch1
+RESET SESSION AUTHORIZATION;
+GRANT CREATE ON SCHEMA sts_sch1 TO regress_stats_user1;
+SET SESSION AUTHORIZATION regress_stats_user1;
+CREATE STATISTICS sts_sch1.pass ON a, b FROM sts_sch1.tbl;
+-- re-creating statistics via ALTER TABLE bypasses checks for CREATE on schema
+RESET SESSION AUTHORIZATION;
+REVOKE CREATE ON SCHEMA sts_sch1 FROM regress_stats_user1;
+SET SESSION AUTHORIZATION regress_stats_user1;
+ALTER TABLE sts_sch1.tbl ALTER COLUMN a TYPE SMALLINT;
 -- Tidy up
 DROP OPERATOR <<< (int, int);
 DROP FUNCTION op_leak(int, int);
@@ -3383,4 +3400,6 @@ NOTICE:  drop cascades to 3 other objects
 DETAIL:  drop cascades to table tststats.priv_test_parent_tbl
 drop cascades to table tststats.priv_test_tbl
 drop cascades to view tststats.priv_test_view
+DROP SCHEMA sts_sch1 CASCADE;
+NOTICE:  drop cascades to table sts_sch1.tbl
 DROP USER regress_stats_user1;

src/test/regress/sql/stats_ext.sql

@@ -1729,6 +1729,24 @@ SELECT statistics_name, most_common_vals FROM pg_stats_ext x
 SELECT statistics_name, most_common_vals FROM pg_stats_ext_exprs x
     WHERE tablename = 'stats_ext_tbl' ORDER BY ROW(x.*);
 
+-- CREATE STATISTICS checks for CREATE on the schema
+RESET SESSION AUTHORIZATION;
+CREATE SCHEMA sts_sch1 CREATE TABLE sts_sch1.tbl (a INT, b INT);
+GRANT USAGE ON SCHEMA sts_sch1 TO regress_stats_user1;
+ALTER TABLE sts_sch1.tbl OWNER TO regress_stats_user1;
+SET SESSION AUTHORIZATION regress_stats_user1;
+CREATE STATISTICS sts_sch1.fail ON a, b FROM sts_sch1.tbl;
+RESET SESSION AUTHORIZATION;
+GRANT CREATE ON SCHEMA sts_sch1 TO regress_stats_user1;
+SET SESSION AUTHORIZATION regress_stats_user1;
+CREATE STATISTICS sts_sch1.pass ON a, b FROM sts_sch1.tbl;
+
+-- re-creating statistics via ALTER TABLE bypasses checks for CREATE on schema
+RESET SESSION AUTHORIZATION;
+REVOKE CREATE ON SCHEMA sts_sch1 FROM regress_stats_user1;
+SET SESSION AUTHORIZATION regress_stats_user1;
+ALTER TABLE sts_sch1.tbl ALTER COLUMN a TYPE SMALLINT;
+
 -- Tidy up
 DROP OPERATOR <<< (int, int);
 DROP FUNCTION op_leak(int, int);
@@ -1737,4 +1755,5 @@ DROP FUNCTION op_leak(record, record);
 RESET SESSION AUTHORIZATION;
 DROP TABLE stats_ext_tbl;
 DROP SCHEMA tststats CASCADE;
+DROP SCHEMA sts_sch1 CASCADE;
 DROP USER regress_stats_user1;