stm32/modusocket: Fix NULL deref when accept() an unbound socket.

1 files changed, 5 insertions, 0 deletions

diff --git a/ports/stm32/modusocket.c b/ports/stm32/modusocket.c
index 7503ecbd6..5a1633113 100644
--- a/ports/stm32/modusocket.c
+++ b/ports/stm32/modusocket.c
@@ -125,6 +125,11 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(socket_listen_obj, socket_listen);
 STATIC mp_obj_t socket_accept(mp_obj_t self_in) {
     mod_network_socket_obj_t *self = MP_OBJ_TO_PTR(self_in);
 
+    if (self->nic == MP_OBJ_NULL) {
+        // not bound
+        mp_raise_OSError(MP_EINVAL);
+    }
+
     // create new socket object
     // starts with empty NIC so that finaliser doesn't run close() method if accept() fails
     mod_network_socket_obj_t *socket2 = m_new_obj_with_finaliser(mod_network_socket_obj_t);