Fix use-after-free bug with AfterTriggersTableData.storeslot

AfterTriggerSaveEvent() wrongly allocates the slot in execution-span
memory context, whereas the correct thing is to allocate it in
a transaction-span context, because that's where the enclosing
AfterTriggersTableData instance belongs into.

Backpatch to 12 (the test back to 11, where it works well with no code
changes, and it's good to have to confirm that the case was previously
well supported); this bug seems introduced by commit ff11e7f4b9ae.

Reported-by: Bertrand Drouvot 
Author: Amit Langote 
Discussion: https://postgr.es/m/39a71864-b120-5a5c-8cc5-c632b6f16761@amazon.com

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 95752fa31d8a5c963bed0c54e9937504520126fa..751c465bff68ab1d6b96ba6bdcb8f99409c96aa4 100644 (file)
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -3832,6 +3832,8 @@ static void AfterTriggerExecute(EState *estate,
                                TupleTableSlot *trig_tuple_slot2);
 static AfterTriggersTableData *GetAfterTriggersTableData(Oid relid,
                                                         CmdType cmdType);
+static TupleTableSlot *GetAfterTriggersStoreSlot(AfterTriggersTableData *table,
+                                                TupleDesc tupdesc);
 static void AfterTriggerFreeQuery(AfterTriggersQueryData *qs);
 static SetConstraintState SetConstraintStateCreate(int numalloc);
 static SetConstraintState SetConstraintStateCopy(SetConstraintState state);
@@ -4634,6 +4636,31 @@ GetAfterTriggersTableData(Oid relid, CmdType cmdType)
    return table;
 }
 
+/*
+ * Returns a TupleTableSlot suitable for holding the tuples to be put
+ * into AfterTriggersTableData's transition table tuplestores.
+ */
+static TupleTableSlot *
+GetAfterTriggersStoreSlot(AfterTriggersTableData *table,
+                         TupleDesc tupdesc)
+{
+   /* Create it if not already done. */
+   if (!table->storeslot)
+   {
+       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().
+        */
+       oldcxt = MemoryContextSwitchTo(CurTransactionContext);
+       table->storeslot = MakeSingleTupleTableSlot(tupdesc, &TTSOpsVirtual);
+       MemoryContextSwitchTo(oldcxt);
+   }
+
+   return table->storeslot;
+}
 
 /*
  * MakeTransitionCaptureState
@@ -4922,6 +4949,8 @@ AfterTriggerFreeQuery(AfterTriggersQueryData *qs)
        table->new_tuplestore = NULL;
        if (ts)
            tuplestore_end(ts);
+       if (table->storeslot)
+           ExecDropSingleTupleTableSlot(table->storeslot);
    }
 
    /*
@@ -5771,17 +5800,10 @@ AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
 
            if (map != NULL)
            {
+               AfterTriggersTableData *table = transition_capture->tcs_private;
                TupleTableSlot *storeslot;
 
-               storeslot = transition_capture->tcs_private->storeslot;
-               if (!storeslot)
-               {
-                   storeslot = ExecAllocTableSlot(&estate->es_tupleTable,
-                                                  map->outdesc,
-                                                  &TTSOpsVirtual);
-                   transition_capture->tcs_private->storeslot = storeslot;
-               }
-
+               storeslot = GetAfterTriggersStoreSlot(table, map->outdesc);
                execute_attr_map_slot(map->attrMap, oldslot, storeslot);
                tuplestore_puttupleslot(old_tuplestore, storeslot);
            }
@@ -5801,18 +5823,10 @@ AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
                                        original_insert_tuple);
            else if (map != NULL)
            {
+               AfterTriggersTableData *table = transition_capture->tcs_private;
                TupleTableSlot *storeslot;
 
-               storeslot = transition_capture->tcs_private->storeslot;
-
-               if (!storeslot)
-               {
-                   storeslot = ExecAllocTableSlot(&estate->es_tupleTable,
-                                                  map->outdesc,
-                                                  &TTSOpsVirtual);
-                   transition_capture->tcs_private->storeslot = storeslot;
-               }
-
+               storeslot = GetAfterTriggersStoreSlot(table, map->outdesc);
                execute_attr_map_slot(map->attrMap, newslot, storeslot);
                tuplestore_puttupleslot(new_tuplestore, storeslot);
            }

diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
index 316eefdb6b430cc47d34261aba2a5d73f6d1433b..38406a28796a98fdbed3e93fb5c7b60c83afe4fc 100644 (file)
--- a/src/test/regress/expected/triggers.out
+++ b/src/test/regress/expected/triggers.out
@@ -3083,3 +3083,62 @@ drop table self_ref;
 drop function dump_insert();
 drop function dump_update();
 drop function dump_delete();
+-- verify transition table conversion slot's lifetime
+-- https://postgr.es/m/[email protected]
+create table convslot_test_parent (col1 text primary key);
+create table convslot_test_child (col1 text primary key,
+   foreign key (col1) references convslot_test_parent(col1) on delete cascade on update cascade
+);
+alter table convslot_test_child add column col2 text not null default 'tutu';
+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()
+returns trigger
+language plpgsql
+AS $$
+begin
+raise notice 'trigger = %, old_table = %',
+          TG_NAME,
+          (select string_agg(old_table::text, ', ' order by col1) from old_table);
+return null;
+end; $$;
+create or replace function trigger_function2()
+returns trigger
+language plpgsql
+AS $$
+begin
+raise notice 'trigger = %, new table = %',
+          TG_NAME,
+          (select string_agg(new_table::text, ', ' order by col1) from new_table);
+return null;
+end; $$;
+create trigger but_trigger after update on convslot_test_child
+referencing new table as new_table
+for each statement execute function trigger_function2();
+update convslot_test_parent set col1 = col1 || '1';
+NOTICE:  trigger = but_trigger, new table = (11,tutu), (31,tutu)
+create or replace function trigger_function3()
+returns trigger
+language plpgsql
+AS $$
+begin
+raise notice 'trigger = %, old_table = %, new table = %',
+          TG_NAME,
+          (select string_agg(old_table::text, ', ' order by col1) from old_table),
+          (select string_agg(new_table::text, ', ' order by col1) from new_table);
+return null;
+end; $$;
+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();
+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();
+delete from convslot_test_parent;
+NOTICE:  trigger = bdt_trigger, old_table = (111,tutu), (311,tutu)
+drop table convslot_test_child, convslot_test_parent;

diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
index 4caa11d63b0559fff51200eff90013e54cb22cb0..f81ce18109aa0fcd3e301cf790570752681b705e 100644 (file)
--- a/src/test/regress/sql/triggers.sql
+++ b/src/test/regress/sql/triggers.sql
@@ -2296,3 +2296,68 @@ drop table self_ref;
 drop function dump_insert();
 drop function dump_update();
 drop function dump_delete();
+
+-- verify transition table conversion slot's lifetime
+-- https://postgr.es/m/[email protected]
+create table convslot_test_parent (col1 text primary key);
+create table convslot_test_child (col1 text primary key,
+   foreign key (col1) references convslot_test_parent(col1) on delete cascade on update cascade
+);
+
+alter table convslot_test_child add column col2 text not null default 'tutu';
+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()
+returns trigger
+language plpgsql
+AS $$
+begin
+raise notice 'trigger = %, old_table = %',
+          TG_NAME,
+          (select string_agg(old_table::text, ', ' order by col1) from old_table);
+return null;
+end; $$;
+
+create or replace function trigger_function2()
+returns trigger
+language plpgsql
+AS $$
+begin
+raise notice 'trigger = %, new table = %',
+          TG_NAME,
+          (select string_agg(new_table::text, ', ' order by col1) from new_table);
+return null;
+end; $$;
+
+create trigger but_trigger after update on convslot_test_child
+referencing new table as new_table
+for each statement execute function trigger_function2();
+
+update convslot_test_parent set col1 = col1 || '1';
+
+create or replace function trigger_function3()
+returns trigger
+language plpgsql
+AS $$
+begin
+raise notice 'trigger = %, old_table = %, new table = %',
+          TG_NAME,
+          (select string_agg(old_table::text, ', ' order by col1) from old_table),
+          (select string_agg(new_table::text, ', ' order by col1) from new_table);
+return null;
+end; $$;
+
+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();
+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();
+delete from convslot_test_parent;
+
+drop table convslot_test_child, convslot_test_parent;