[libgrss] src: Add missing NULL checks for XML elements

[Philip Withnall <pwithnall src gnome org>]

commit 9a9376c1c09486a450ecbf89c3c9483954bd7ae9
Author: Philip Withnall <withnall endlessm com>
Date:   Wed Dec 21 16:49:14 2016 +0000

    src: Add missing NULL checks for XML elements
    
    If the loop to skip blank elements ends up reading the entire document,
    cur will be set to NULL, and the following code (which dereferences its
    elements) will crash. Avoid that by checking cur again.
    
    Coverity IDs: 1388544, 1388545, 1388548
    
    https://bugzilla.gnome.org/show_bug.cgi?id=776115

 src/feed-atom-handler.c |    2 +-
 src/feed-pie-handler.c  |    2 +-
 src/feed-rss-handler.c  |    9 +++++----
 3 files changed, 7 insertions(+), 6 deletions(-)
---
diff --git a/src/feed-atom-handler.c b/src/feed-atom-handler.c
index 7a20662..f8cf47c 100644
--- a/src/feed-atom-handler.c
+++ b/src/feed-atom-handler.c
@@ -782,7 +782,7 @@ feed_atom_handler_parse (FeedHandler *self, GrssFeedChannel *feed, xmlDocPtr doc
        parser = FEED_ATOM_HANDLER (self);
 
        while (TRUE) {
-               if (xmlStrcmp (cur->name, BAD_CAST"feed")) {
+               if (!cur || xmlStrcmp (cur->name, BAD_CAST"feed")) {
                        g_set_error (error, FEED_ATOM_HANDLER_ERROR, FEED_ATOM_HANDLER_PARSE_ERROR, "Could 
not find Atom 1.0 header!");
                        break;
                }
diff --git a/src/feed-pie-handler.c b/src/feed-pie-handler.c
index b15e192..26c4738 100644
--- a/src/feed-pie-handler.c
+++ b/src/feed-pie-handler.c
@@ -326,7 +326,7 @@ feed_pie_handler_parse (FeedHandler *self, GrssFeedChannel *feed, xmlDocPtr doc,
                cur = cur->next;
 
        while (TRUE) {
-               if (xmlStrcmp (cur->name, BAD_CAST"feed")) {
+               if (!cur || xmlStrcmp (cur->name, BAD_CAST"feed")) {
                        g_set_error (error, FEED_PIE_HANDLER_ERROR, FEED_PIE_HANDLER_PARSE_ERROR, "Could not 
find Atom/PIE header!");
                        break;
                }
diff --git a/src/feed-rss-handler.c b/src/feed-rss-handler.c
index 879e9ff..efcc300 100644
--- a/src/feed-rss-handler.c
+++ b/src/feed-rss-handler.c
@@ -452,16 +452,17 @@ feed_rss_handler_parse (FeedHandler *self, GrssFeedChannel *feed, xmlDocPtr doc,
        while (cur && xmlIsBlankNode (cur))
                cur = cur->next;
 
-       if (!xmlStrcmp (cur->name, BAD_CAST"rss")) {
+       if (cur && !xmlStrcmp (cur->name, BAD_CAST"rss")) {
                cur = cur->xmlChildrenNode;
                rdf = FALSE;
        }
-       else if (!xmlStrcmp (cur->name, BAD_CAST"rdf") ||
-                !xmlStrcmp (cur->name, BAD_CAST"RDF")) {
+       else if (cur &&
+                (!xmlStrcmp (cur->name, BAD_CAST"rdf") ||
+                 !xmlStrcmp (cur->name, BAD_CAST"RDF"))) {
                cur = cur->xmlChildrenNode;
                rdf = TRUE;
        }
-       else if (!xmlStrcmp (cur->name, BAD_CAST"Channel")) {
+       else if (cur && !xmlStrcmp (cur->name, BAD_CAST"Channel")) {
                rdf = FALSE;
        }
        else {