[WIN32K]

- Do not dereference hook objects when it's not needed.
 - Avoid use after free.
CORE-8698 #resolve

svn path=/trunk/; revision=64954

reactos/win32ss/user/ntuser/hook.c

@@ -1294,12 +1294,14 @@ IntUnhookWindowsHook(int HookId, HOOKPROC pfnFilterProc)
        {
           Hook = CONTAINING_RECORD(pElement, HOOK, Chain);
 
+          /* Get the next element now, we might free the hook in what follows */
+          pElement = Hook->Chain.Flink;
+
           if (Hook->Proc == pfnFilterProc)
           {
              if (Hook->head.pti == pti)
              {
                 IntRemoveHook(Hook);
-                UserDereferenceObject(Hook);
                 return TRUE;
              }
              else
@@ -1308,8 +1310,6 @@ IntUnhookWindowsHook(int HookId, HOOKPROC pfnFilterProc)
                 return FALSE;
              }
           }
-
-          pElement = Hook->Chain.Flink;
        }
     }
     return FALSE;