From 15907c36236d638437a1ed3efc0794fda2c9ad22 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 21 Feb 2011 21:18:13 -0500 Subject: Fix dangling-pointer problem in before-row update trigger processing. ExecUpdate checked for whether ExecBRUpdateTriggers had returned a new tuple value by seeing if the returned tuple was pointer-equal to the old one. But the "old one" was in estate->es_junkFilter's result slot, which would be scribbled on if we had done an EvalPlanQual update in response to a concurrent update of the target tuple; therefore we were comparing a dangling pointer to a live one. Given the right set of circumstances we could get a false match, resulting in not forcing the tuple to be stored in the slot we thought it was stored in. In the case reported by Maxim Boguk in bug #5798, this led to "cannot extract system attribute from virtual tuple" failures when trying to do "RETURNING ctid". I believe there is a very-low-probability chance of more serious errors, such as generating incorrect index entries based on the original rather than the trigger-modified version of the row. In HEAD, change all of ExecBRInsertTriggers, ExecIRInsertTriggers, ExecBRUpdateTriggers, and ExecIRUpdateTriggers so that they continue to have similar APIs. In the back branches I just changed ExecBRUpdateTriggers, since there is no bug in the ExecBRInsertTriggers case. --- src/backend/executor/nodeModifyTable.c | 27 +++++---------------------- 1 file changed, 5 insertions(+), 22 deletions(-) (limited to 'src/backend/executor') diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c index f4b2b16b69e..ee6eef74f7a 100644 --- a/src/backend/executor/nodeModifyTable.c +++ b/src/backend/executor/nodeModifyTable.c @@ -453,31 +453,14 @@ ExecUpdate(ItemPointer tupleid, if (resultRelInfo->ri_TrigDesc && resultRelInfo->ri_TrigDesc->n_before_row[TRIGGER_EVENT_UPDATE] > 0) { - HeapTuple newtuple; - - newtuple = ExecBRUpdateTriggers(estate, epqstate, resultRelInfo, - tupleid, tuple); + slot = ExecBRUpdateTriggers(estate, epqstate, resultRelInfo, + tupleid, slot); - if (newtuple == NULL) /* "do nothing" */ + if (slot == NULL) /* "do nothing" */ return NULL; - if (newtuple != tuple) /* modified by Trigger(s) */ - { - /* - * Put the modified tuple into a slot for convenience of routines - * below. We assume the tuple was allocated in per-tuple memory - * context, and therefore will go away by itself. The tuple table - * slot should not try to clear it. - */ - TupleTableSlot *newslot = estate->es_trig_tuple_slot; - TupleDesc tupdesc = RelationGetDescr(resultRelationDesc); - - if (newslot->tts_tupleDescriptor != tupdesc) - ExecSetSlotDescriptor(newslot, tupdesc); - ExecStoreTuple(newtuple, newslot, InvalidBuffer, false); - slot = newslot; - tuple = newtuple; - } + /* trigger might have changed tuple */ + tuple = ExecMaterializeSlot(slot); } /* -- cgit v1.2.3