SocketStats: tighten up

* Avoid undefined behaviour when copying/clearing `mbed_stats_socket_t`.
  As it contains a `SocketAddress`, memset and memcpy should not be used.
* Avoid array overrun when `mbed_stats_socket_get_each` is passed a
  count greater than `nsapi.socket-stats-max-count`.
* Remove `const` from internal `stats_new_socket_entry` method to avoid
  const-losing cast.

Author: kjbracey

features/netsocket/SocketStats.cpp

@@ -21,7 +21,6 @@
 #include "rtos/Kernel.h"
 #endif
 
-#include <string.h>
 #include <stdlib.h>
 
 #if MBED_CONF_NSAPI_SOCKET_STATS_ENABLED
@@ -42,28 +41,24 @@ int SocketStats::get_entry_position(const Socket *const reference_id)
 size_t SocketStats::mbed_stats_socket_get_each(mbed_stats_socket_t *stats, size_t count)
 {
     MBED_ASSERT(stats != NULL);
-    size_t i = 0;
-    memset(stats, 0, count * sizeof(mbed_stats_socket_t));
+    size_t j;
     _mutex->lock();
-    for (uint32_t j = 0; j < count; j++) {
-        if (_stats[j].reference_id) {
-            memcpy(&stats[i], &_stats[j], sizeof(mbed_stats_socket_t));
-            i++;
-        }
+    for (j = 0; j < count && j < _size; j++) {
+        stats[j] = _stats[j];
     }
     _mutex->unlock();
-    return i;
+    return j;
 }
 
-void SocketStats::stats_new_socket_entry(const Socket *const reference_id)
+void SocketStats::stats_new_socket_entry(Socket *const reference_id)
 {
     _mutex->lock();
     if (get_entry_position(reference_id) >= 0) {
         // Duplicate entry
         MBED_WARNING1(MBED_MAKE_ERROR(MBED_MODULE_NETWORK_STATS, MBED_ERROR_CODE_INVALID_INDEX), "Duplicate socket Reference ID ", reference_id);
     } else if (_size < MBED_CONF_NSAPI_SOCKET_STATS_MAX_COUNT) {
         // Add new entry
-        _stats[_size].reference_id = (Socket *)reference_id;
+        _stats[_size].reference_id = reference_id;
         _size++;
     } else {
         int position = -1;
@@ -80,8 +75,8 @@ void SocketStats::stats_new_socket_entry(const Socket *const reference_id)
         if (-1 == position) {
             MBED_ERROR(MBED_MAKE_ERROR(MBED_MODULE_NETWORK_STATS, MBED_ERROR_CODE_OUT_OF_RESOURCES), "List full with all open sockets");
         }
-        memset(&_stats[position], 0, sizeof(mbed_stats_socket_t));
-        _stats[position].reference_id = (Socket *)reference_id;
+        _stats[position] = {};
+        _stats[position].reference_id = reference_id;
     }
     _mutex->unlock();
 }

features/netsocket/SocketStats.h

@@ -93,7 +93,7 @@ class SocketStats {
      *         the socket creation count exceeds `MBED_CONF_NSAPI_SOCKET_STATS_MAX_COUNT`.
      *
      */
-    void stats_new_socket_entry(const Socket *reference_id);
+    void stats_new_socket_entry(Socket *reference_id);
 
     /** Updates the state of the socket and records `tick_last_change`.
      *  API used by socket (TCP or UDP) layers only, not to be used by application.
@@ -162,7 +162,7 @@ inline size_t SocketStats::mbed_stats_socket_get_each(mbed_stats_socket_t *, siz
     return 0;
 }
 
-inline void SocketStats::stats_new_socket_entry(const Socket *)
+inline void SocketStats::stats_new_socket_entry(Socket *)
 {
 }