From f73fa5a470b4cf850ad404b63c3e352d179d40b0 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 18 Sep 2023 14:27:47 -0400 Subject: [PATCH] Don't crash if cursor_to_xmlschema is used on a non-data-returning Portal. cursor_to_xmlschema() assumed that any Portal must have a tupDesc, which is not so. Add a defensive check. It's plausible that this mistake occurred because of the rather poorly chosen name of the lookup function SPI_cursor_find(), which in such cases is returning something that isn't very much like a cursor. Add some documentation to try to forestall future errors of the same ilk. Report and patch by Boyu Yang (docs changes by me). Back-patch to all supported branches. Discussion: https://postgr.es/m/dd343010-c637-434c-a8cb-418f53bda3b8.yangboyu.yby@alibaba-inc.com --- doc/src/sgml/spi.sgml | 13 +++++++++++++ src/backend/utils/adt/xml.c | 4 ++++ 2 files changed, 17 insertions(+) diff --git a/doc/src/sgml/spi.sgml b/doc/src/sgml/spi.sgml index 16c3ab71e8..47f4b5b431 100644 --- a/doc/src/sgml/spi.sgml +++ b/doc/src/sgml/spi.sgml @@ -2727,6 +2727,19 @@ Portal SPI_cursor_find(const char * name) NULL if none was found + + + Notes + + + Beware that this function can return a Portal object + that does not have cursor-like properties; for example it might not + return tuples. If you simply pass the Portal pointer + to other SPI functions, they can defend themselves against such + cases, but caution is appropriate when directly inspecting + the Portal. + + diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c index 866d0d649a..2300c7ebf3 100644 --- a/src/backend/utils/adt/xml.c +++ b/src/backend/utils/adt/xml.c @@ -3012,6 +3012,10 @@ cursor_to_xmlschema(PG_FUNCTION_ARGS) ereport(ERROR, (errcode(ERRCODE_UNDEFINED_CURSOR), errmsg("cursor \"%s\" does not exist", name))); + if (portal->tupDesc == NULL) + ereport(ERROR, + (errcode(ERRCODE_INVALID_CURSOR_STATE), + errmsg("portal \"%s\" does not return tuples", name))); xmlschema = _SPI_strdup(map_sql_table_to_xmlschema(portal->tupDesc, InvalidOid, nulls,