Fix Bug 9853: 'Lua: trying to get/access a Preference before its registered causes a segfault'

Accessing a pref before it's registered causes a segfault, because prefs_p->next
is not being checked for NULL in wslua_proto.c:Prefs__index().

Change-Id: I270978ddb9238a9e8d2c533a96fc01ee0df385c7
Reviewed-on: https://code.wireshark.org/review/563
Reviewed-by: Evan Huus <eapache@gmail.com>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>

1 files changed, 14 insertions, 9 deletions

diff --git a/epan/wslua/wslua_proto.c b/epan/wslua/wslua_proto.c
index a7716d9b19..1f1e320cc9 100644
--- a/epan/wslua/wslua_proto.c
+++ b/epan/wslua/wslua_proto.c
@@ -305,18 +305,18 @@ WSLUA_METAMETHOD Prefs__newindex(lua_State* L) {
             luaL_error(L,"a preference named %s exists already",name);
             return 0;
         }
-    /*
+        /*
          * Make sure that only lower-case ASCII letters, numbers,
          * underscores, and dots appear in the preference name.
-     */
-    for (c = name; *c != '\0'; c++) {
-        if (!isascii((guchar)*c) ||
-           (!islower((guchar)*c) && !isdigit((guchar)*c) && *c != '_' && *c != '.'))
-        {
-            luaL_error(L,"illegal preference name \"%s\", only lower-case ASCII letters, numbers, underscores and dots may be used",name);
-            return 0;
+         */
+        for (c = name; *c != '\0'; c++) {
+            if (!isascii((guchar)*c) ||
+               (!islower((guchar)*c) && !isdigit((guchar)*c) && *c != '_' && *c != '.'))
+            {
+                luaL_error(L,"illegal preference name \"%s\", only lower-case ASCII letters, numbers, underscores and dots may be used",name);
+                return 0;
+            }
         }
-    }
 
         if ( ! p->next) {
             p->next = pref;
@@ -400,6 +400,11 @@ WSLUA_METAMETHOD Prefs__index(lua_State* L) {
 
     if (! ( name && prefs_p ) ) return 0;
 
+    if (!prefs_p->next) {
+        luaL_error(L,"No preference is registered yet");
+        return 0;
+    }
+
     prefs_p = prefs_p->next;
 
     do {