Thread: pgsql: Fix theoretical bug in tuplesort
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 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/41469253e970b539a4ae75226dd4f226b7b2bc8c Modified Files -------------- src/backend/utils/sort/tuplesort.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
... btw, wouldn't it be advisable to set stup->tuple to NULL
after dropping the referenced storage?
regards, tom lane
On Tue, 13 Jul 2021 at 12:42, Tom Lane <tgl@sss.pgh.pa.us> wrote: > > ... btw, wouldn't it be advisable to set stup->tuple to NULL > after dropping the referenced storage? I think that's probably a good idea. I'll adjust that now... David