Avoid "you don't own a lock of type ExclusiveLock" in GRANT TABLESPACE.

This WARNING appeared because SearchSysCacheLocked1() read
cc_relisshared before catcache initialization, when the field is false
unconditionally.  On the basis of reading false there, it constructed a
locktag as though pg_tablespace weren't relisshared.  Only shared
catalogs could be affected, and only GRANT TABLESPACE was affected in
practice.  SearchSysCacheLocked1() callers use one other shared-relation
syscache, DATABASEOID.  DATABASEOID is initialized by the end of
CheckMyDatabase(), making the problem unreachable for pg_database.

Back-patch to v13 (all supported versions).  This has no known impact
before v16, where ExecGrant_common() first appeared.  Earlier branches
avoid trouble by having a separate ExecGrant_Tablespace() that doesn't
use LOCKTAG_TUPLE.  However, leaving this unfixed in v15 could ensnare a
future back-patch of a SearchSysCacheLocked1() call.

Reported by Aya Iwata.

Discussion: https://postgr.es/m/OS7PR01MB11964507B5548245A7EE54E70EA212@OS7PR01MB11964.jpnprd01.prod.outlook.com

diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index 50c9440f7923e8a3b473b8fdefe6d2e47f13c385..88c47a999650582f5f38de1443dbd2c9ccd758a2 100644 (file)
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -287,11 +287,9 @@ HeapTuple
 SearchSysCacheLocked1(int cacheId,
                      Datum key1)
 {
+   CatCache   *cache = SysCache[cacheId];
    ItemPointerData tid;
    LOCKTAG     tag;
-   Oid         dboid =
-       SysCache[cacheId]->cc_relisshared ? InvalidOid : MyDatabaseId;
-   Oid         reloid = cacheinfo[cacheId].reloid;
 
    /*----------
     * Since inplace updates may happen just before our LockTuple(), we must
@@ -343,8 +341,15 @@ SearchSysCacheLocked1(int cacheId,
 
        tid = tuple->t_self;
        ReleaseSysCache(tuple);
-       /* like: LockTuple(rel, &tid, lockmode) */
-       SET_LOCKTAG_TUPLE(tag, dboid, reloid,
+
+       /*
+        * Do like LockTuple(rel, &tid, lockmode).  While cc_relisshared won't
+        * change from one iteration to another, it may have been a temporary
+        * "false" until our first SearchSysCache1().
+        */
+       SET_LOCKTAG_TUPLE(tag,
+                         cache->cc_relisshared ? InvalidOid : MyDatabaseId,
+                         cache->cc_reloid,
                          ItemPointerGetBlockNumber(&tid),
                          ItemPointerGetOffsetNumber(&tid));
        (void) LockAcquire(&tag, lockmode, false, false);

diff --git a/src/test/regress/expected/tablespace.out b/src/test/regress/expected/tablespace.out
index 9aabb8534974151b4a40e79170245667036340ab..9c561395970dbf9f2e932b5cba1fa1a949d2c9d3 100644 (file)
--- a/src/test/regress/expected/tablespace.out
+++ b/src/test/regress/expected/tablespace.out
@@ -927,6 +927,11 @@ ALTER INDEX testschema.part_a_idx SET TABLESPACE pg_default;
 -- Fail, not empty
 DROP TABLESPACE regress_tblspace;
 ERROR:  tablespace "regress_tblspace" is not empty
+-- Adequate cache initialization before GRANT
+\c -
+BEGIN;
+GRANT ALL ON TABLESPACE regress_tblspace TO PUBLIC;
+ROLLBACK;
 CREATE ROLE regress_tablespace_user1 login;
 CREATE ROLE regress_tablespace_user2 login;
 GRANT USAGE ON SCHEMA testschema TO regress_tablespace_user2;

diff --git a/src/test/regress/sql/tablespace.sql b/src/test/regress/sql/tablespace.sql
index d274d9615efa7df88d5ec8e863d5102d1358909a..0f9c136d3172e28d3520c909dc63394b41f5007e 100644 (file)
--- a/src/test/regress/sql/tablespace.sql
+++ b/src/test/regress/sql/tablespace.sql
@@ -396,6 +396,12 @@ ALTER INDEX testschema.part_a_idx SET TABLESPACE pg_default;
 -- Fail, not empty
 DROP TABLESPACE regress_tblspace;
 
+-- Adequate cache initialization before GRANT
+\c -
+BEGIN;
+GRANT ALL ON TABLESPACE regress_tblspace TO PUBLIC;
+ROLLBACK;
+
 CREATE ROLE regress_tablespace_user1 login;
 CREATE ROLE regress_tablespace_user2 login;
 GRANT USAGE ON SCHEMA testschema TO regress_tablespace_user2;