v2-0001-Added-support-of-XML_PARSE_HUGE-flag-for-XML-docu.patch

From 88fdf5b7c4da1ed9acb4d5711ef771566edcc39b Mon Sep 17 00:00:00 2001
From: Koval Dmitry <d.koval@postgrespro.ru>
Date: Sun, 14 Jan 2024 21:02:55 +0300
Subject: [PATCH v2] Added support of XML_PARSE_HUGE flag for XML documents

1. PostgreSQL uses functions of libxml2 library without XML_PARSE_HUGE flag.
But in practice, the 10 MB limit is too small.
Using libxml2 library functions with support of XML_PARSE_HUGE flag
increases maximum size allowed for a single text node from 10.000.000 to
1.000.000.000 (see XML_MAX_TEXT_LENGTH macro) which in most cases solves
the problem with insufficient memory.

2. xmlParseBalancedChunkMemory function (haven't argument for pass
XML_PARSE_HUGE flag) was replaced to xmlNewNode+xmlParseInNodeContext
functions (create a fake node and pass the XML_PARSE_HUGE flag to
xmlParseInNodeContext function).

3. Replaced the xmlParseMemory and xmlSubstituteEntitiesDefault functions,
which marked as deprecated [1].

[1] https://gnome.pages.gitlab.gnome.org/libxml2/devhelp/libxml2-parser.html
---
 contrib/xml2/xpath.c        | 10 ++++++----
 contrib/xml2/xslt_proc.c    | 10 ++++++----
 src/backend/utils/adt/xml.c | 35 +++++++++++++++++++++++++++--------
 3 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/contrib/xml2/xpath.c b/contrib/xml2/xpath.c
index a692dc6be8..a2cec95f3f 100644
--- a/contrib/xml2/xpath.c
+++ b/contrib/xml2/xpath.c
@@ -74,7 +74,6 @@ pgxml_parser_init(PgXmlStrictness strictness)
 	/* Initialize libxml */
 	xmlInitParser();
 
-	xmlSubstituteEntitiesDefault(1);
 	xmlLoadExtDtdDefaultValue = 1;
 
 	return xmlerrcxt;
@@ -380,8 +379,9 @@ pgxml_xpath(text *document, xmlChar *xpath, xpath_workspace *workspace)
 
 	PG_TRY();
 	{
-		workspace->doctree = xmlParseMemory((char *) VARDATA_ANY(document),
-											docsize);
+		workspace->doctree = xmlReadMemory((char *) VARDATA_ANY(document),
+										   docsize, NULL, NULL,
+										   XML_PARSE_HUGE | XML_PARSE_NOENT);
 		if (workspace->doctree != NULL)
 		{
 			workspace->ctxt = xmlXPathNewContext(workspace->doctree);
@@ -624,7 +624,9 @@ xpath_table(PG_FUNCTION_ARGS)
 
 			/* Parse the document */
 			if (xmldoc)
-				doctree = xmlParseMemory(xmldoc, strlen(xmldoc));
+				doctree = xmlReadMemory(xmldoc, strlen(xmldoc),
+										NULL, NULL,
+										XML_PARSE_HUGE | XML_PARSE_NOENT);
 			else				/* treat NULL as not well-formed */
 				doctree = NULL;
 
diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c
index 2189bca86f..9cbc05db1a 100644
--- a/contrib/xml2/xslt_proc.c
+++ b/contrib/xml2/xslt_proc.c
@@ -85,16 +85,18 @@ xslt_process(PG_FUNCTION_ARGS)
 		bool		xslt_sec_prefs_error;
 
 		/* Parse document */
-		doctree = xmlParseMemory((char *) VARDATA_ANY(doct),
-								 VARSIZE_ANY_EXHDR(doct));
+		doctree = xmlReadMemory((char *) VARDATA_ANY(doct),
+								VARSIZE_ANY_EXHDR(doct), NULL, NULL,
+								XML_PARSE_HUGE | XML_PARSE_NOENT);
 
 		if (doctree == NULL)
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
 						"error parsing XML document");
 
 		/* Same for stylesheet */
-		ssdoc = xmlParseMemory((char *) VARDATA_ANY(ssheet),
-							   VARSIZE_ANY_EXHDR(ssheet));
+		ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet),
+							  VARSIZE_ANY_EXHDR(ssheet), NULL, NULL,
+							  XML_PARSE_HUGE | XML_PARSE_NOENT);
 
 		if (ssdoc == NULL)
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_EXTERNAL_ROUTINE_EXCEPTION,
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 191dd2d1e2..9402e645f7 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -1688,7 +1688,7 @@ xml_doctype_in_content(const xmlChar *str)
  * xmloption_arg, but a DOCTYPE node in the input can force DOCUMENT mode).
  *
  * If parsed_nodes isn't NULL and the input is not an XML document, the list
- * of parsed nodes from the xmlParseBalancedChunkMemory call will be returned
+ * of parsed nodes from the xmlParseInNodeContext call will be returned
  * to *parsed_nodes.
  *
  * Errors normally result in ereport(ERROR), but if escontext is an
@@ -1795,7 +1795,7 @@ xml_parse(text *data, XmlOptionType xmloption_arg,
 			doc = xmlCtxtReadDoc(ctxt, utf8string,
 								 NULL,
 								 "UTF-8",
-								 XML_PARSE_NOENT | XML_PARSE_DTDATTR
+								 XML_PARSE_NOENT | XML_PARSE_DTDATTR | XML_PARSE_HUGE
 								 | (preserve_whitespace ? 0 : XML_PARSE_NOBLANKS));
 			if (doc == NULL || xmlerrcxt->err_occurred)
 			{
@@ -1828,10 +1828,29 @@ xml_parse(text *data, XmlOptionType xmloption_arg,
 			/* allow empty content */
 			if (*(utf8string + count))
 			{
-				res_code = xmlParseBalancedChunkMemory(doc, NULL, NULL, 0,
-													   utf8string + count,
-													   parsed_nodes);
-				if (res_code != 0 || xmlerrcxt->err_occurred)
+				const char *data;
+				xmlNodePtr	root;
+				xmlParserErrors xml_error;
+				xmlNodePtr	lst;
+
+				data = (const char *) (utf8string + count);
+
+				/*
+				 * Create a fake root node. The xmlNewDoc function creates an
+				 * XML document without any nodes. But we need one to call the
+				 * xmlParseInNodeContext function.
+				 */
+				root = xmlNewNode(NULL, (const xmlChar *) "content-root");
+				if (root == NULL || xmlerrcxt->err_occurred)
+					xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+								"could not allocate xml node");
+				xmlDocSetRootElement(doc, root);
+
+				/* Try to parse string with using root node context. */
+				xml_error = xmlParseInNodeContext(root, data, strlen(data),
+												  XML_PARSE_HUGE,
+												  parsed_nodes ? parsed_nodes : &lst);
+				if (xml_error != XML_ERR_OK || xmlerrcxt->err_occurred)
 				{
 					xml_errsave(escontext, xmlerrcxt,
 								ERRCODE_INVALID_XML_CONTENT,
@@ -4344,7 +4363,7 @@ xpath_internal(text *xpath_expr_text, xmltype *data, ArrayType *namespaces,
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
 						"could not allocate parser context");
 		doc = xmlCtxtReadMemory(ctxt, (char *) string + xmldecl_len,
-								len - xmldecl_len, NULL, NULL, 0);
+								len - xmldecl_len, NULL, NULL, XML_PARSE_HUGE);
 		if (doc == NULL || xmlerrcxt->err_occurred)
 			xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"could not parse XML document");
@@ -4675,7 +4694,7 @@ XmlTableSetDocument(TableFuncScanState *state, Datum value)
 
 	PG_TRY();
 	{
-		doc = xmlCtxtReadMemory(xtCxt->ctxt, (char *) xstr, length, NULL, NULL, 0);
+		doc = xmlCtxtReadMemory(xtCxt->ctxt, (char *) xstr, length, NULL, NULL, XML_PARSE_HUGE);
 		if (doc == NULL || xtCxt->xmlerrcxt->err_occurred)
 			xml_ereport(xtCxt->xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT,
 						"could not parse XML document");
-- 
2.40.1.windows.1