Fix null-dereference crash in parse_xml_decl().

parse_xml_decl's header comment says you can pass NULL for any unwanted
output parameter, but it failed to honor this contract for the "standalone"
flag.  The only currently-affected caller is xml_recv, so the net effect is
that sending a binary XML value containing a standalone parameter in its
xml declaration would crash the backend.  Per bug #6044 from Christopher
Dillard.

In passing, remove useless initializations of parse_xml_decl's output
parameters in xml_parse.

Back-patch to 8.3, where this code was introduced.

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index ee82d46..702b9e3 100644 (file)
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -1067,13 +1067,15 @@ parse_xml_decl(const xmlChar *str, size_t *lenp,
                if (xmlStrncmp(p, (xmlChar *) "'yes'", 5) == 0 ||
                        xmlStrncmp(p, (xmlChar *) "\"yes\"", 5) == 0)
                {
-                       *standalone = 1;
+                       if (standalone)
+                               *standalone = 1;
                        p += 5;
                }
                else if (xmlStrncmp(p, (xmlChar *) "'no'", 4) == 0 ||
                                 xmlStrncmp(p, (xmlChar *) "\"no\"", 4) == 0)
                {
-                       *standalone = 0;
+                       if (standalone)
+                               *standalone = 0;
                        p += 4;
                }
                else
@@ -1218,8 +1220,8 @@ xml_parse(text *data, XmlOptionType xmloption_arg, bool preserve_whitespace,
                {
                        int                     res_code;
                        size_t          count;
-                       xmlChar    *version = NULL;
-                       int                     standalone = -1;
+                       xmlChar    *version;
+                       int                     standalone;
 
                        res_code = parse_xml_decl(utf8string,
                                                                          &count, &version, NULL, &standalone);