[xml] [PATCH] fix memory leak xml header encoding field in combination with XML_PARSE_IGNORE_ENC

[Bart De Schuymer <deschuyb b-virtual org>]

Hello,

When the xml parser encounters an xml encoding in an xml header while configured with option XML_PARSE_IGNORE_ENC, it fails to free memory allocated for storing the encoding.

The patch below fixes this.

How to reproduce:

1. Change doc/examples/parse4.c to add xmlCtxtUseOptions(ctxt, XML_PARSE_IGNORE_ENC); after the call to xmlCreatePushParserCtxt.

2. Rebuild
3. run the following command from the top libxml2 directory: LD_LIBRARY_PATH=.libs/ valgrind --leak-check=full ./doc/examples/.libs/parse4 ./test.xml , where test.xml contains following input:

<?xml version="1.0" encoding="UTF-81" ?><hi/>
valgrind will report:
==1964== 10 bytes in 1 blocks are definitely lost in loss record 1 of 1
==1964==    at 0x4C272DB: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1964==    by 0x4E88497: xmlParseEncName (parser.c:10224)
==1964==    by 0x4E888FE: xmlParseEncodingDecl (parser.c:10295)
==1964==    by 0x4E89630: xmlParseXMLDecl (parser.c:10534)
==1964==    by 0x4E8B737: xmlParseTryOrFinish (parser.c:11293)
==1964==    by 0x4E8E775: xmlParseChunk (parser.c:12283)

Best regards,
Bart

Signed-off-by: Bart De Schuymer <bart at amplidata com>

diff --git a/parser.c b/parser.c
index 9347ac9..3ce1eb0 100644
--- a/parser.c
+++ b/parser.c
@@ -10318,8 +10318,10 @@ xmlParseEncodingDecl(xmlParserCtxtPtr ctxt) {
         /*
          * Non standard parsing, allowing the user to ignore encoding
          */
-        if (ctxt->options & XML_PARSE_IGNORE_ENC)
-            return(encoding);
+        if (ctxt->options & XML_PARSE_IGNORE_ENC) {
+            xmlFree((xmlChar *) encoding);
+            return(NULL);
+        }
 
     /*
      * UTF-16 encoding stwich has already taken place at this stage,