From 204f646a22f294a359ec463c128d01e1bc9117c5 Mon Sep 17 00:00:00 2001 From: David Rowley Date: Tue, 13 Jul 2021 12:42:43 +1200 Subject: [PATCH] Fix theoretical bug in tuplesort This fixes a theoretical bug in tuplesort.c which, if a bounded sort was used in combination with a byval Datum sort (tuplesort_begin_datum), when switching the sort to a bounded heap in make_bounded_heap(), we'd call free_sort_tuple(). The problem was that when sorting Datums of a byval type, the tuple is NULL and free_sort_tuple() would free the memory for it regardless of that. This would result in a crash. Here we fix that simply by adding a check to see if the tuple is NULL before trying to disassociate and free any memory belonging to it. The reason this bug is only theoretical is that nowhere in the current code base do we do tuplesort_set_bound() when performing a Datum sort. However, let's backpatch a fix for this as if any extension uses the code in this way then it's likely to cause problems. Author: Ronan Dunklau Discussion: https://postgr.es/m/CAApHDvpdoqNC5FjDb3KUTSMs5dg6f+XxH4Bg_dVcLi8UYAG3EQ@mail.gmail.com Backpatch-through: 9.6, oldest supported version --- src/backend/utils/sort/tuplesort.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c index cbda911f46..52c5ca8b8a 100644 --- a/src/backend/utils/sort/tuplesort.c +++ b/src/backend/utils/sort/tuplesort.c @@ -4697,6 +4697,9 @@ leader_takeover_tapes(Tuplesortstate *state) static void free_sort_tuple(Tuplesortstate *state, SortTuple *stup) { - FREEMEM(state, GetMemoryChunkSpace(stup->tuple)); - pfree(stup->tuple); + if (stup->tuple) + { + FREEMEM(state, GetMemoryChunkSpace(stup->tuple)); + pfree(stup->tuple); + } }