postgres.git / summary / log / commit / refs

commit    e6e50ada07bbbbea2a68597d0bf7f795b0dc1269
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Mon Sep 18 18:27:47 2023 +0000
First released in: 17.0, 11.22, 12.17, 13.13, 14.10, 15.5, 16.1

    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 55ca90ad58f..493c74b4e5d 100644
--- a/doc/src/sgml/spi.sgml
+++ b/doc/src/sgml/spi.sgml
@@ -2092,6 +2092,19 @@ Portal SPI_cursor_find(const char * <parameter>name</parameter>)
    <symbol>NULL</symbol> if none was found
   </para>
  </refsect1>
+
+ <refsect1>
+  <title>Notes</title>
+
+  <para>
+   Beware that this function can return a <type>Portal</type> object
+   that does not have cursor-like properties; for example it might not
+   return tuples.  If you simply pass the <type>Portal</type> pointer
+   to other SPI functions, they can defend themselves against such
+   cases, but caution is appropriate when directly inspecting
+   the <type>Portal</type>.
+  </para>
+ </refsect1>
 </refentry>
 
 <!-- *********************************************** -->
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 0b40c53e247..7fc9669fb09 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -2762,6 +2762,10 @@ 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,


[parent: c5b7f791dab9]