[libxml2] encoding: fix memleak in xmlRegisterCharEncodingHandler()

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 649d02eaa419fa72ae6b131718a4ac77063d7a5a
Author: Xiaoming Ni <nixiaoming huawei com>
Date:   Mon Dec 7 20:19:53 2020 +0800

    encoding: fix memleak in xmlRegisterCharEncodingHandler()
    
    The return type of xmlRegisterCharEncodingHandler() is void. The invoker
    cannot determine whether xmlRegisterCharEncodingHandler() is executed
    successfully. when nbCharEncodingHandler >= MAX_ENCODING_HANDLERS, the
    "handler" is not added to the array "handlers". As a result, the memory
    of "handler" cannot be managed and released: memory leakage.
    
    so add "xmlfree(handler)" to fix memory leakage on the failure branch of
    xmlRegisterCharEncodingHandler().
    
    Reported-by: wuqing <wuqing30 huawei com>
    Signed-off-by: Xiaoming Ni <nixiaoming huawei com>

 encoding.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)
---
diff --git a/encoding.c b/encoding.c
index 264f60bb..d67c16d9 100644
--- a/encoding.c
+++ b/encoding.c
@@ -1488,16 +1488,25 @@ xmlRegisterCharEncodingHandler(xmlCharEncodingHandlerPtr handler) {
     if ((handler == NULL) || (handlers == NULL)) {
         xmlEncodingErr(XML_I18N_NO_HANDLER,
                "xmlRegisterCharEncodingHandler: NULL handler !\n", NULL);
-       return;
+        goto free_handler;
     }
 
     if (nbCharEncodingHandler >= MAX_ENCODING_HANDLERS) {
         xmlEncodingErr(XML_I18N_EXCESS_HANDLER,
        "xmlRegisterCharEncodingHandler: Too many handler registered, see %s\n",
                       "MAX_ENCODING_HANDLERS");
-       return;
+        goto free_handler;
     }
     handlers[nbCharEncodingHandler++] = handler;
+    return;
+
+free_handler:
+    if (handler != NULL) {
+        if (handler->name != NULL) {
+            xmlFree(handler->name);
+        }
+        xmlFree(handler);
+    }
 }
 
 /**