From 50dd1eb9505880304a3ae55f4b64a8c596883c69 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C5=82awek=20Piotrowski?= <sentinel@atteo.com>
Date: Sat, 6 Oct 2018 09:29:30 +0200
Subject: [PATCH] Fix hard-fault when socket created using accept() is closed

When socket created  using accept() is closed by calling the close()
method, "delete this" is executed which triggers the destructor call
on TCPSocket which in turn calls close() once again. Because _stack
is already 0 this results in a hard-fault.

Add a check that skips the rest of the close() method is the _stack
is already 0.
---
 .../features/netsocket/InternetSocket/test_InternetSocket.cpp | 1 +
 features/netsocket/InternetSocket.cpp                         | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/UNITTESTS/features/netsocket/InternetSocket/test_InternetSocket.cpp b/UNITTESTS/features/netsocket/InternetSocket/test_InternetSocket.cpp
index 859f1eb964..bf3424869f 100644
--- a/UNITTESTS/features/netsocket/InternetSocket/test_InternetSocket.cpp
+++ b/UNITTESTS/features/netsocket/InternetSocket/test_InternetSocket.cpp
@@ -222,6 +222,7 @@ TEST_F(TestInternetSocket, getsockopt)
 TEST_F(TestInternetSocket, sigio)
 {
     callback_is_called = false;
+    socket->open((NetworkStack *)&stack);
     socket->sigio(mbed::callback(my_callback));
     socket->close(); // Trigger event;
     EXPECT_EQ(callback_is_called, true);
diff --git a/features/netsocket/InternetSocket.cpp b/features/netsocket/InternetSocket.cpp
index 948e25374a..cc793450a2 100644
--- a/features/netsocket/InternetSocket.cpp
+++ b/features/netsocket/InternetSocket.cpp
@@ -56,6 +56,10 @@ nsapi_error_t InternetSocket::close()
     _lock.lock();
 
     nsapi_error_t ret = NSAPI_ERROR_OK;
+    if (!_stack)  {
+        return ret;
+    }
+
     if (_socket) {
         _stack->socket_attach(_socket, 0, 0);
         nsapi_socket_t socket = _socket;