From f10fdf7ad4a88fea319a1a271c85a375c3370497 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Fri, 29 May 2015 11:01:03 -0600
Subject: [PATCH] Networking: Add a test to see a device pointer is still valid

---
 net/devif/devif_callback.c     | 26 +++++++++++++++++++++++---
 net/netdev/Make.defs           |  4 ++--
 net/netdev/netdev.h            | 14 ++++++++++++++
 net/netdev/netdev_findbyname.c |  4 ++--
 4 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/net/devif/devif_callback.c b/net/devif/devif_callback.c
index 11f1bdfb6b..997d81ac70 100644
--- a/net/devif/devif_callback.c
+++ b/net/devif/devif_callback.c
@@ -49,6 +49,7 @@
 #include <nuttx/net/net.h>
 #include <nuttx/net/netdev.h>
 
+#include "netdev/netdev.h"
 #include "devif/devif.h"
 
 /****************************************************************************
@@ -123,6 +124,16 @@ FAR struct devif_callback_s *
       
       if (dev)
         {
+          /* Verify that the device is valid */
+
+          if (!netdev_verify(dev))
+            {
+              /* No.. release the callback structure and fail */
+
+              devif_callback_free(NULL, NULL, list);
+              return NULL;
+            }
+
            ret->nxtdev  = dev->d_devcb;
            dev->d_devcb = ret;
         }
@@ -181,10 +192,15 @@ void devif_callback_free(FAR struct net_driver_s *dev,
         }
 #endif
 
-      /* Find the callback structure in the device event list */
+      /* Remove the callback structure from the device notification list if
+       * it is supposed to be in the device notification list AND if the
+       * device pointer is still valid.
+       */
 
-      if (dev)
+      if (dev && netdev_verify(dev))
         {
+          /* Find the callback structure in the device event list */
+
           for (prev = NULL, curr = dev->d_devcb;
                curr && curr != cb;
                prev = curr, curr = curr->nxtdev);
@@ -205,10 +221,14 @@ void devif_callback_free(FAR struct net_driver_s *dev,
             }
         }
 
-      /* Find the callback structure in the connection event list */
+      /* Remove the callback structure from the data notification list if
+       * it is supposed to be in the data notification list.
+       */
 
       if (list)
         {
+          /* Find the callback structure in the connection event list */
+
           for (prev = NULL, curr = *list;
                curr && curr != cb;
                prev = curr, curr = curr->nxtconn);
diff --git a/net/netdev/Make.defs b/net/netdev/Make.defs
index 50fffc8bbc..40c08f9642 100644
--- a/net/netdev/Make.defs
+++ b/net/netdev/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # net/netdev/Make.defs
 #
-#   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2014-2015 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -38,7 +38,7 @@
 NETDEV_CSRCS += netdev_register.c netdev_ioctl.c netdev_txnotify.c
 NETDEV_CSRCS += netdev_findbyname.c netdev_findbyaddr.c netdev_count.c
 NETDEV_CSRCS += netdev_foreach.c netdev_unregister.c netdev_sem.c
-NETDEV_CSRCS += netdev_carrier.c netdev_default.c
+NETDEV_CSRCS += netdev_carrier.c netdev_default.c netdev_verify.c
 
 ifeq ($(CONFIG_NET_RXAVAIL),y)
 NETDEV_CSRCS += netdev_rxnotify.c
diff --git a/net/netdev/netdev.h b/net/netdev/netdev.h
index 5377c2d2d8..8c9bd1077d 100644
--- a/net/netdev/netdev.h
+++ b/net/netdev/netdev.h
@@ -43,6 +43,7 @@
 #include <nuttx/config.h>
 
 #include <sys/types.h>
+#include <stdbool.h>
 
 #include <nuttx/net/ip.h>
 
@@ -124,6 +125,19 @@ void netdev_semgive(void);
 void netdev_ifup(FAR struct net_driver_s *dev);
 void netdev_ifdown(FAR struct net_driver_s *dev);
 
+/****************************************************************************
+ * Function: netdev_verify
+ *
+ * Description:
+ *   Verify that the specified device still exists
+ *
+ * Assumptions:
+ *   The caller has locked the network.
+ *
+ ****************************************************************************/
+
+bool netdev_verify(FAR struct net_driver_s *dev);
+
 /****************************************************************************
  * Function: netdev_findbyname
  *
diff --git a/net/netdev/netdev_findbyname.c b/net/netdev/netdev_findbyname.c
index e428872d8a..d9d44a9701 100644
--- a/net/netdev/netdev_findbyname.c
+++ b/net/netdev/netdev_findbyname.c
@@ -89,9 +89,9 @@
  *
  ****************************************************************************/
 
-FAR struct net_driver_s *netdev_findbyname(const char *ifname)
+FAR struct net_driver_s *netdev_findbyname(FAR const char *ifname)
 {
-  struct net_driver_s *dev;
+  FAR struct net_driver_s *dev;
   if (ifname)
     {
       netdev_semtake();