Fix tupdesc lifespan bug with AfterTriggersTableData.storeslot.

tglsfdc · tglsfdc · commit c82766c0298a · 2022-09-25T17:10:58.000-04:00
Commit 25936fd adjusted things so that the "storeslot" we use for remapping trigger tuples would have adequate lifespan, but it neglected to consider the lifespan of the tuple descriptor that the slot depends on. It turns out that in at least some cases, the tupdesc we are passing is a refcounted tupdesc, and the refcount for the slot's reference can get assigned to a resource owner having different lifespan than the slot does. That leads to an error like "tupdesc reference 0x7fdef236a1b8 is not owned by resource owner SubTransaction". Worse, because of a second oversight in the same commit, we'd try to free the same tupdesc refcount again while cleaning up after that error, leading to recursive errors and an "ERRORDATA_STACK_SIZE exceeded" PANIC. To fix the initial problem, let's just make a non-refcounted copy of the tupdesc we're supposed to use. That seems likely to guard against additional problems, since there's no strong reason for this code to assume that what it's given is a refcounted tupdesc; in which case there's an independent hazard of the tupdesc having shorter lifespan than the slot does. (I didn't bother trying to free said copy, since it should go away anyway when the (sub) transaction context is cleaned up.) The other issue can be fixed by making the code added to AfterTriggerFreeQuery work like the rest of that function, ie be sure that it doesn't try to free the same slot twice in the event of recursive error cleanup. While here, also clean up minor stylistic issues in the test case added by 25936fd: don't use "create or replace function", as any name collision within the tests is likely to have ill effects that that won't mask; and don't use function names as generic as trigger_function1, especially if you're not going to drop them at the end of the test stanza. Per bug #17607 from Thomas Mc Kay. Back-patch to v12, as the previous fix was. Discussion: https://postgr.es/m/17607-bd8ccc81226f7f80@postgresql.org
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
@@ -4827,11 +4827,13 @@ GetAfterTriggersStoreSlot(AfterTriggersTableData *table,
 		MemoryContext oldcxt;
 
 		/*
-		 * We only need this slot only until AfterTriggerEndQuery, but making
-		 * it last till end-of-subxact is good enough.  It'll be freed by
-		 * AfterTriggerFreeQuery().
+		 * We need this slot only until AfterTriggerEndQuery, but making it
+		 * last till end-of-subxact is good enough.  It'll be freed by
+		 * AfterTriggerFreeQuery().  However, the passed-in tupdesc might have
+		 * a different lifespan, so we'd better make a copy of that.
 		 */
 		oldcxt = MemoryContextSwitchTo(CurTransactionContext);
+		tupdesc = CreateTupleDescCopy(tupdesc);
 		table->storeslot = MakeSingleTupleTableSlot(tupdesc, &TTSOpsVirtual);
 		MemoryContextSwitchTo(oldcxt);
 	}
@@ -5150,7 +5152,12 @@ AfterTriggerFreeQuery(AfterTriggersQueryData *qs)
 		if (ts)
 			tuplestore_end(ts);
 		if (table->storeslot)
-			ExecDropSingleTupleTableSlot(table->storeslot);
+		{
+			TupleTableSlot *slot = table->storeslot;
+
+			table->storeslot = NULL;
+			ExecDropSingleTupleTableSlot(slot);
+		}
 	}
 
 	/*
diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
@@ -3468,7 +3468,7 @@ insert into convslot_test_parent(col1) values ('1');
 insert into convslot_test_child(col1) values ('1');
 insert into convslot_test_parent(col1) values ('3');
 insert into convslot_test_child(col1) values ('3');
-create or replace function trigger_function1()
+create function convslot_trig1()
 returns trigger
 language plpgsql
 AS $$
@@ -3478,7 +3478,7 @@ raise notice 'trigger = %, old_table = %',
           (select string_agg(old_table::text, ', ' order by col1) from old_table);
 return null;
 end; $$;
-create or replace function trigger_function2()
+create function convslot_trig2()
 returns trigger
 language plpgsql
 AS $$
@@ -3490,10 +3490,10 @@ return null;
 end; $$;
 create trigger but_trigger after update on convslot_test_child
 referencing new table as new_table
-for each statement execute function trigger_function2();
+for each statement execute function convslot_trig2();
 update convslot_test_parent set col1 = col1 || '1';
 NOTICE:  trigger = but_trigger, new table = (11,tutu), (31,tutu)
-create or replace function trigger_function3()
+create function convslot_trig3()
 returns trigger
 language plpgsql
 AS $$
@@ -3506,16 +3506,42 @@ return null;
 end; $$;
 create trigger but_trigger2 after update on convslot_test_child
 referencing old table as old_table new table as new_table
-for each statement execute function trigger_function3();
+for each statement execute function convslot_trig3();
 update convslot_test_parent set col1 = col1 || '1';
 NOTICE:  trigger = but_trigger, new table = (111,tutu), (311,tutu)
 NOTICE:  trigger = but_trigger2, old_table = (11,tutu), (31,tutu), new table = (111,tutu), (311,tutu)
 create trigger bdt_trigger after delete on convslot_test_child
 referencing old table as old_table
-for each statement execute function trigger_function1();
+for each statement execute function convslot_trig1();
 delete from convslot_test_parent;
 NOTICE:  trigger = bdt_trigger, old_table = (111,tutu), (311,tutu)
 drop table convslot_test_child, convslot_test_parent;
+drop function convslot_trig1();
+drop function convslot_trig2();
+drop function convslot_trig3();
+-- Bug #17607: variant of above in which trigger function raises an error;
+-- we don't see any ill effects unless trigger tuple requires mapping
+create table convslot_test_parent (id int primary key, val int)
+partition by range (id);
+create table convslot_test_part (val int, id int not null);
+alter table convslot_test_parent
+  attach partition convslot_test_part for values from (1) to (1000);
+create function convslot_trig4() returns trigger as
+$$begin raise exception 'BOOM!'; end$$ language plpgsql;
+create trigger convslot_test_parent_update
+    after update on convslot_test_parent
+    referencing old table as old_rows new table as new_rows
+    for each statement execute procedure convslot_trig4();
+insert into convslot_test_parent (id, val) values (1, 2);
+begin;
+savepoint svp;
+update convslot_test_parent set val = 3;  -- error expected
+ERROR:  BOOM!
+CONTEXT:  PL/pgSQL function convslot_trig4() line 1 at RAISE
+rollback to savepoint svp;
+rollback;
+drop table convslot_test_parent;
+drop function convslot_trig4();
 -- Test trigger renaming on partitioned tables
 create table grandparent (id int, primary key (id)) partition by range (id);
 create table middle partition of grandparent for values from (1) to (10)
diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
@@ -2615,7 +2615,7 @@ insert into convslot_test_child(col1) values ('1');
 insert into convslot_test_parent(col1) values ('3');
 insert into convslot_test_child(col1) values ('3');
 
-create or replace function trigger_function1()
+create function convslot_trig1()
 returns trigger
 language plpgsql
 AS $$
@@ -2626,7 +2626,7 @@ raise notice 'trigger = %, old_table = %',
 return null;
 end; $$;
 
-create or replace function trigger_function2()
+create function convslot_trig2()
 returns trigger
 language plpgsql
 AS $$
@@ -2639,11 +2639,11 @@ end; $$;
 
 create trigger but_trigger after update on convslot_test_child
 referencing new table as new_table
-for each statement execute function trigger_function2();
+for each statement execute function convslot_trig2();
 
 update convslot_test_parent set col1 = col1 || '1';
 
-create or replace function trigger_function3()
+create function convslot_trig3()
 returns trigger
 language plpgsql
 AS $$
@@ -2657,15 +2657,48 @@ end; $$;
 
 create trigger but_trigger2 after update on convslot_test_child
 referencing old table as old_table new table as new_table
-for each statement execute function trigger_function3();
+for each statement execute function convslot_trig3();
 update convslot_test_parent set col1 = col1 || '1';
 
 create trigger bdt_trigger after delete on convslot_test_child
 referencing old table as old_table
-for each statement execute function trigger_function1();
+for each statement execute function convslot_trig1();
 delete from convslot_test_parent;
 
 drop table convslot_test_child, convslot_test_parent;
+drop function convslot_trig1();
+drop function convslot_trig2();
+drop function convslot_trig3();
+
+-- Bug #17607: variant of above in which trigger function raises an error;
+-- we don't see any ill effects unless trigger tuple requires mapping
+
+create table convslot_test_parent (id int primary key, val int)
+partition by range (id);
+
+create table convslot_test_part (val int, id int not null);
+
+alter table convslot_test_parent
+  attach partition convslot_test_part for values from (1) to (1000);
+
+create function convslot_trig4() returns trigger as
+$$begin raise exception 'BOOM!'; end$$ language plpgsql;
+
+create trigger convslot_test_parent_update
+    after update on convslot_test_parent
+    referencing old table as old_rows new table as new_rows
+    for each statement execute procedure convslot_trig4();
+
+insert into convslot_test_parent (id, val) values (1, 2);
+
+begin;
+savepoint svp;
+update convslot_test_parent set val = 3;  -- error expected
+rollback to savepoint svp;
+rollback;
+
+drop table convslot_test_parent;
+drop function convslot_trig4();
 
 -- Test trigger renaming on partitioned tables
 create table grandparent (id int, primary key (id)) partition by range (id);
