[libxml2] Fix potential NULL pointer dereferences in regexp code

[Daniel Veillard <veillard src gnome org>]

commit 2671b013d88b381d8a9139ef85381234aafc5ce0
Author: Gaurav <g gupta samsung com>
Date:   Wed Sep 11 14:59:06 2013 +0800

    Fix potential NULL pointer dereferences in regexp code
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707749
    
    Fix 3 cases where we might dereference NULL

 xmlregexp.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/xmlregexp.c b/xmlregexp.c
index 1f9911c..8e63d74 100644
--- a/xmlregexp.c
+++ b/xmlregexp.c
@@ -3162,8 +3162,10 @@ xmlFARegExecRollBack(xmlRegExecCtxtPtr exec) {
            exec->status = -6;
            return;
        }
-       memcpy(exec->counts, exec->rollbacks[exec->nbRollbacks].counts,
+       if (exec->counts) {
+           memcpy(exec->counts, exec->rollbacks[exec->nbRollbacks].counts,
               exec->comp->nbCounters * sizeof(int));
+       }
     }
 
 #ifdef DEBUG_REGEXP_EXEC
@@ -4091,7 +4093,7 @@ rollback:
             */
            exec->determinist = 0;
            xmlFARegExecRollBack(exec);
-           if (exec->status == 0) {
+           if ((exec->inputStack != NULL ) && (exec->status == 0)) {
                value = exec->inputStack[exec->index].value;
                data = exec->inputStack[exec->index].data;
 #ifdef DEBUG_PUSH
@@ -4306,7 +4308,7 @@ xmlRegExecGetValues(xmlRegExecCtxtPtr exec, int err,
                    (*nbval)++;
                }
            } else {
-                if ((exec->comp->states[trans->to] != NULL) &&
+                if ((exec->comp != NULL) && (exec->comp->states[trans->to] != NULL) &&
                    (exec->comp->states[trans->to]->type !=
                     XML_REGEXP_SINK_STATE)) {
                    if (atom->neg)