Thread

[PATCH 1/2] Fix libxml string leak in contrib/xml2 xpath_list

Andrey Chernyy <andrey.cherny@tantorlabs.com> — 2026-05-25T19:12:02Z

xmlXPathCastNodeToString() returns a libxml-allocated xmlChar *, but
pgxmlNodeSetToText() passed it directly to xmlBufferWriteCHAR() in the
plain separator path.  Since xmlBufferWriteCHAR() copies the string
rather than taking ownership, successful xpath_list() calls leaked one
string per emitted node.

Store the cast result locally and free it with xmlFree() after writing it
to the buffer.
---
 contrib/xml2/xpath.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/contrib/xml2/xpath.c b/contrib/xml2/xpath.c
index 7bf477e0c3f..94819961787 100644
--- a/contrib/xml2/xpath.c
+++ b/contrib/xml2/xpath.c
@@ -147,6 +147,7 @@ pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
 {
 	volatile xmlBufferPtr buf = NULL;
 	xmlChar    *volatile result = NULL;
+	xmlChar    *volatile str = NULL;
 	PgXmlErrorContext *xmlerrcxt;
 
 	/* spin up some error handling */
@@ -172,8 +173,14 @@ pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
 			{
 				if (plainsep != NULL)
 				{
-					xmlBufferWriteCHAR(buf,
-									   xmlXPathCastNodeToString(nodeset->nodeTab[i]));
+					str = xmlXPathCastNodeToString(nodeset->nodeTab[i]);
+					if (str == NULL || pg_xml_error_occurred(xmlerrcxt))
+						xml_ereport(xmlerrcxt, ERROR, ERRCODE_OUT_OF_MEMORY,
+									"could not allocate node text");
+
+					xmlBufferWriteCHAR(buf, str);
+					xmlFree(str);
+					str = NULL;
 
 					/* If this isn't the last entry, write the plain sep. */
 					if (i < (nodeset->nodeNr) - 1)
@@ -216,6 +223,8 @@ pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
 	}
 	PG_CATCH();
 	{
+		if (str)
+			xmlFree(str);
 		if (buf)
 			xmlBufferFree(buf);
 
-- 
2.54.0


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