Don't assume that WM_DESTROY is the last message to be received by a

window.  Since the child windows are still alive and kicking by the
time the parent receives WM_DESTROY, it's still possible to receive
other messages after WM_DESTROY.

If we free any window specific data when handling WM_DESTROY, we
should reset the window data field as well, and check if we have a
valid pointer when retrieving the window data field later.

ticket: 5584

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@19627 dc483132-0cff-0310-8789-dd5450dbe970

22 files changed, 282 insertions, 36 deletions

diff --git a/src/windows/identity/plugins/krb4/krb4configdlg.c b/src/windows/identity/plugins/krb4/krb4configdlg.c
index 338cf7fa8..309bf542b 100644
--- a/src/windows/identity/plugins/krb4/krb4configdlg.c
+++ b/src/windows/identity/plugins/krb4/krb4configdlg.c
@@ -113,6 +113,9 @@ krb4_ids_config_proc(HWND hwnd,
         d = (k4_ids_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         if (HIWORD(wParam) == BN_CLICKED) {
             k4_ids_check_mod(hwnd, d);
         }
@@ -122,6 +125,9 @@ krb4_ids_config_proc(HWND hwnd,
         d = (k4_ids_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         if (HIWORD(wParam) == WMCFG_APPLY) {
             k4_ids_write_params(hwnd, d);
         }
@@ -131,7 +137,11 @@ krb4_ids_config_proc(HWND hwnd,
         d = (k4_ids_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
-        PFREE(d);
+        if (d) {
+            PFREE(d);
+            SetWindowLongPtr(hwnd, DWLP_USER, (LONG_PTR) 0);
+        }
+
         break;
     }
 
@@ -297,6 +307,9 @@ krb4_id_config_proc(HWND hwnd,
             d = (k4_id_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
 
+            if (d == NULL)
+                break;
+
             if (wParam == MAKEWPARAM(IDC_CFG_GETTIX,
                                      BN_CLICKED)) {
                 int gettix = 0;
@@ -321,7 +334,7 @@ krb4_id_config_proc(HWND hwnd,
             d = (k4_id_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
 
-            if (!d)
+            if (d == NULL)
                 break;
 
             if (HIWORD(wParam) == WMCFG_APPLY) {
@@ -343,10 +356,12 @@ krb4_id_config_proc(HWND hwnd,
             d = (k4_id_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
 
-            if (!d)
+            if (d == NULL)
                 break;
 
             PFREE(d);
+
+            SetWindowLongPtr(hwnd, DWLP_USER, 0);
         }
         break;
     }
@@ -531,6 +546,7 @@ krb4_confg_proc(HWND hwnd,
 
         if (d) {
             PFREE(d);
+            SetWindowLongPtr(hwnd, DWLP_USER, (LONG_PTR) 0);
         }
 
         break;
diff --git a/src/windows/identity/plugins/krb4/krb4newcreds.c b/src/windows/identity/plugins/krb4/krb4newcreds.c
index c2d477e0e..9c200b618 100644
--- a/src/windows/identity/plugins/krb4/krb4newcreds.c
+++ b/src/windows/identity/plugins/krb4/krb4newcreds.c
@@ -389,6 +389,9 @@ INT_PTR CALLBACK k4_nc_dlg_proc(HWND hwnd,
                 d = (k4_dlg_data *) (LONG_PTR)
                     GetWindowLongPtr(hwnd, DWLP_USER);
 
+                if (d == NULL)
+                    break;
+
                 k4_update_data(d);
 
                 if (LOWORD(wParam) == IDC_NCK4_OBTAIN) {
@@ -404,6 +407,10 @@ INT_PTR CALLBACK k4_nc_dlg_proc(HWND hwnd,
         {
             d = (k4_dlg_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
+
+            if (d == NULL)
+                break;
+
             k4_handle_wmnc_notify(d, wParam, lParam);
         }
         break;
@@ -413,9 +420,13 @@ INT_PTR CALLBACK k4_nc_dlg_proc(HWND hwnd,
             d = (k4_dlg_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
 
+            if (d == NULL)
+                break;
+
             d->nct->aux = 0;
 
             PFREE(d);
+            SetWindowLongPtr(hwnd, DWLP_USER, 0);
         }
         break;
     }
diff --git a/src/windows/identity/plugins/krb5/krb5configcc.c b/src/windows/identity/plugins/krb5/krb5configcc.c
index b2b498e68..13c5ac86b 100644
--- a/src/windows/identity/plugins/krb5/krb5configcc.c
+++ b/src/windows/identity/plugins/krb5/krb5configcc.c
@@ -354,6 +354,10 @@ k5_ccconfig_dlgproc(HWND hwnd,
     case WM_COMMAND:
         d = (k5_ccc_dlg_data *) (DWORD_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
+
+        if (d == NULL)
+            break;
+
         switch(wParam) {
         case MAKEWPARAM(IDC_CFG_ADD, BN_CLICKED):
             {
@@ -543,15 +547,22 @@ k5_ccconfig_dlgproc(HWND hwnd,
         d = (k5_ccc_dlg_data *) (DWORD_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         k5_free_file_ccs(&d->work);
         k5_free_file_ccs(&d->save);
         PFREE(d);
+        SetWindowLongPtr(hwnd, DWLP_USER, 0);
         return TRUE;
 
     case KHUI_WM_CFG_NOTIFY:
         d = (k5_ccc_dlg_data *) (DWORD_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         switch(HIWORD(wParam)) {
         case WMCFG_APPLY:
             if (k5_ccc_get_mod(d)) {
diff --git a/src/windows/identity/plugins/krb5/krb5configid.c b/src/windows/identity/plugins/krb5/krb5configid.c
index b5af1c2b2..e730a4bb0 100644
--- a/src/windows/identity/plugins/krb5/krb5configid.c
+++ b/src/windows/identity/plugins/krb5/krb5configid.c
@@ -324,6 +324,9 @@ k5_id_tab_dlgproc(HWND hwnd,
         d = (k5_id_dlg_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         if (HIWORD(wParam) == EN_CHANGE ||
             HIWORD(wParam) == BN_CLICKED)
             k5_id_check_mod(hwnd, d);
@@ -333,6 +336,9 @@ k5_id_tab_dlgproc(HWND hwnd,
         d = (k5_id_dlg_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         if (HIWORD(wParam) == WMCFG_APPLY) {
             k5_id_write_params(hwnd, d);
         }
@@ -342,6 +348,9 @@ k5_id_tab_dlgproc(HWND hwnd,
         d = (k5_id_dlg_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         khui_tracker_kill_controls(&d->tc_life);
         khui_tracker_kill_controls(&d->tc_renew);
 
@@ -349,6 +358,7 @@ k5_id_tab_dlgproc(HWND hwnd,
             kcdb_identity_release(d->ident);
 
         PFREE(d);
+        SetWindowLongPtr(hwnd, DWLP_USER, 0);
         break;
     }
     return FALSE;
diff --git a/src/windows/identity/plugins/krb5/krb5configids.c b/src/windows/identity/plugins/krb5/krb5configids.c
index 8d6afd473..4699f056a 100644
--- a/src/windows/identity/plugins/krb5/krb5configids.c
+++ b/src/windows/identity/plugins/krb5/krb5configids.c
@@ -221,6 +221,9 @@ k5_ids_tab_dlgproc(HWND hwnd,
         d = (k5_ids_dlg_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         if (HIWORD(wParam) == EN_CHANGE) {
             k5_ids_check_mod(d);
         } else if (HIWORD(wParam) == BN_CLICKED) {
@@ -245,6 +248,10 @@ k5_ids_tab_dlgproc(HWND hwnd,
     case KHUI_WM_CFG_NOTIFY:
         d = (k5_ids_dlg_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
+
+        if (d == NULL)
+            break;
+
         if (HIWORD(wParam) == WMCFG_APPLY) {
             k5_ids_write_params(d);
         }
@@ -254,6 +261,9 @@ k5_ids_tab_dlgproc(HWND hwnd,
         d = (k5_ids_dlg_data *) (LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
 
+        if (d == NULL)
+            break;
+
         khui_tracker_kill_controls(&d->tc_life);
         khui_tracker_kill_controls(&d->tc_renew);
         khui_tracker_kill_controls(&d->tc_life_min);
@@ -262,9 +272,13 @@ k5_ids_tab_dlgproc(HWND hwnd,
         khui_tracker_kill_controls(&d->tc_renew_max);
 
         PFREE(d);
+
+        SetWindowLongPtr(hwnd, DWLP_USER, 0);
+
         break;
     }
     return FALSE;
 }
 
 
+
diff --git a/src/windows/identity/plugins/krb5/krb5newcreds.c b/src/windows/identity/plugins/krb5/krb5newcreds.c
index d2458fe50..b382096a0 100644
--- a/src/windows/identity/plugins/krb5/krb5newcreds.c
+++ b/src/windows/identity/plugins/krb5/krb5newcreds.c
@@ -122,6 +122,7 @@ k5_handle_wm_destroy(HWND hwnd,
     }
 
     PFREE(d);
+    SetWindowLongPtr(hwnd, DWLP_USER, 0);
 
     return TRUE;
 }
@@ -184,6 +185,9 @@ k5_handle_wmnc_notify(HWND hwnd,
             d = (k5_dlg_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
 
+            if (d == NULL)
+                return TRUE;
+
             if (d->nc->subtype == KMSG_CRED_NEW_CREDS) {
                 khui_tracker_reposition(&d->tc_lifetime);
                 khui_tracker_reposition(&d->tc_renew);
@@ -201,6 +205,9 @@ k5_handle_wmnc_notify(HWND hwnd,
             d = (k5_dlg_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
 
+            if (d == NULL)
+                return TRUE;
+
             if (d->nc->subtype == KMSG_CRED_PASSWORD)
                 return TRUE;
 
@@ -249,6 +256,10 @@ k5_handle_wmnc_notify(HWND hwnd,
 
             d = (k5_dlg_data *)(LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
+
+            if (d == NULL)
+                return TRUE;
+
             nc = d->nc;
             l = (khui_htwnd_link *) lParam;
 
@@ -277,6 +288,9 @@ k5_handle_wmnc_notify(HWND hwnd,
 
             d = (k5_dlg_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                return TRUE;
+
             nc = d->nc;
             khui_cw_find_type(nc, credtype_id_krb5, &nct);
 
@@ -352,6 +366,8 @@ k5_handle_wmnc_notify(HWND hwnd,
 
             d = (k5_dlg_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                break;
 
             kmq_post_sub_msg(k5_sub, KMSG_CRED, 
                              KMSG_CRED_DIALOG_NEW_IDENTITY, 
@@ -365,6 +381,8 @@ k5_handle_wmnc_notify(HWND hwnd,
 
             d = (k5_dlg_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                break;
 
             if(!d->sync && d->nc->result == KHUI_NC_RESULT_PROCESS) {
                 kmq_post_sub_msg(k5_sub, KMSG_CRED, 
@@ -382,6 +400,8 @@ k5_handle_wmnc_notify(HWND hwnd,
 
             d = (k5_dlg_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                break;
 
             msg = (wchar_t *) lParam;
 
@@ -420,6 +440,8 @@ k5_handle_wm_notify(HWND hwnd,
         pnmh->code == IPN_FIELDCHANGED) {
 
         d = (k5_dlg_data *) (LONG_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return 0;
 
         SendDlgItemMessage(hwnd, IDC_NCK5_PUBLICIP,
                            IPM_GETADDRESS,
@@ -444,6 +466,8 @@ k5_handle_wm_command(HWND hwnd,
     k5_dlg_data * d;
 
     d = (k5_dlg_data *)(LONG_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+    if (d == NULL)
+        return FALSE;
 
     cid = LOWORD(wParam);
     notif = HIWORD(wParam);
diff --git a/src/windows/identity/sample/templates/credprov/config_id.c b/src/windows/identity/sample/templates/credprov/config_id.c
index 850016266..0fd08617b 100644
--- a/src/windows/identity/sample/templates/credprov/config_id.c
+++ b/src/windows/identity/sample/templates/credprov/config_id.c
@@ -88,6 +88,8 @@ config_id_dlgproc(HWND hwnd,
     case KHUI_WM_CFG_NOTIFY:
         d = (config_id_dlg_data *)
             GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            break;
 
         if (HIWORD(wParam) == WMCFG_APPLY) {
             /* TODO: apply changes */
@@ -108,6 +110,7 @@ config_id_dlgproc(HWND hwnd,
                 /* TODO: perform any other required uninitialization */
 
                 free(d);
+                SetWindowLongPtr(hwnd, DWLP_USER, 0);
             }
         }
         break;
diff --git a/src/windows/identity/sample/templates/credprov/config_ids.c b/src/windows/identity/sample/templates/credprov/config_ids.c
index 8d6f0081a..ecc49b20c 100644
--- a/src/windows/identity/sample/templates/credprov/config_ids.c
+++ b/src/windows/identity/sample/templates/credprov/config_ids.c
@@ -72,6 +72,8 @@ config_ids_dlgproc(HWND hwnd,
     case KHUI_WM_CFG_NOTIFY:
         d = (config_ids_dlg_data *)
             GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            break;
 
         if (HIWORD(wParam) == WMCFG_APPLY) {
             /* TODO: apply changes */
@@ -88,6 +90,7 @@ config_ids_dlgproc(HWND hwnd,
             /* TODO: Perform any additional uninitialization */
 
             free (d);
+            SetWindowLongPtr(hwnd, DWLP_USER, 0);
         }
         break;
     }
diff --git a/src/windows/identity/sample/templates/credprov/config_main.c b/src/windows/identity/sample/templates/credprov/config_main.c
index 87a2a15fc..cf8061b81 100644
--- a/src/windows/identity/sample/templates/credprov/config_main.c
+++ b/src/windows/identity/sample/templates/credprov/config_main.c
@@ -71,6 +71,8 @@ config_dlgproc(HWND hwnd,
         {
             d = (config_main_dlg_data *)
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                break;
 
             /* WMCFG_APPLY is the only notification we care about */
 
@@ -88,8 +90,10 @@ config_dlgproc(HWND hwnd,
 
         /* TODO: perform any other required uninitialization here */
 
-        if (d)
+        if (d) {
             free(d);
+            SetWindowLongPtr(hwnd, DWLP_USER);
+        }
 
         break;
     }
diff --git a/src/windows/identity/sample/templates/credprov/credacq.c b/src/windows/identity/sample/templates/credprov/credacq.c
index cd8db44ee..a65686ea4 100644
--- a/src/windows/identity/sample/templates/credprov/credacq.c
+++ b/src/windows/identity/sample/templates/credprov/credacq.c
@@ -147,6 +147,8 @@ handle_wm_command(HWND hwnd, WPARAM wParam, LPARAM lParam) {
     struct nc_dialog_data * d;
 
     d = (struct nc_dialog_data *) GetWindowLongPtr(hwnd, DWLP_USER);
+    if (d == NULL)
+        return FALSE;
 
     /* TODO: handle WM_COMMAND */
     return FALSE;
@@ -165,6 +167,7 @@ handle_wm_destroy(HWND hwnd, WPARAM wParam, LPARAM lParam) {
         d->nct = NULL;
 
         free(d);
+        SetWindowLongPtr(hwnd, DWLP_USER, 0);
     }
 
     /* TODO: Perform any additional uninitialization */
diff --git a/src/windows/identity/ui/cfg_appear_wnd.c b/src/windows/identity/ui/cfg_appear_wnd.c
index c7e9abc25..be7c79fff 100644
--- a/src/windows/identity/ui/cfg_appear_wnd.c
+++ b/src/windows/identity/ui/cfg_appear_wnd.c
@@ -308,6 +308,8 @@ khm_cfg_appearance_proc(HWND hwnd,
 
     case WM_COMMAND:
         d = (dlg_data *) (LONG_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         if (wParam == MAKEWPARAM(IDC_CFG_FONTS, CBN_SELCHANGE)) {
             LRESULT idx;
@@ -417,11 +419,14 @@ khm_cfg_appearance_proc(HWND hwnd,
                 DeleteObject(d->c_font_normal);
 
             PFREE(d);
+            SetWindowLongPtr(hwnd, DWLP_USER, 0);
         }
         return TRUE;
 
     case KHUI_WM_CFG_NOTIFY:
         d = (dlg_data *) (LONG_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         if (HIWORD(wParam) == WMCFG_APPLY) {
             write_params(d);
diff --git a/src/windows/identity/ui/cfg_general_wnd.c b/src/windows/identity/ui/cfg_general_wnd.c
index 1e92947f0..2716818b1 100644
--- a/src/windows/identity/ui/cfg_general_wnd.c
+++ b/src/windows/identity/ui/cfg_general_wnd.c
@@ -332,11 +332,14 @@ khm_cfg_general_proc(HWND hwnd,
         d = (dlg_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
         if (d) {
             PFREE(d);
+            SetWindowLongPtr(hwnd, DWLP_USER, 0);
         }
         return TRUE;
 
     case WM_COMMAND:
         d = (dlg_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         if (HIWORD(wParam) == BN_CLICKED) {
             if (LOWORD(wParam) == IDC_CFG_SHOWLOG) {
@@ -405,6 +408,8 @@ khm_cfg_general_proc(HWND hwnd,
 
     case KHUI_WM_CFG_NOTIFY:
         d = (dlg_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         if (HIWORD(wParam) == WMCFG_APPLY) {
             write_params(d);
diff --git a/src/windows/identity/ui/cfg_identities_wnd.c b/src/windows/identity/ui/cfg_identities_wnd.c
index d45288a3a..ebe61e14d 100644
--- a/src/windows/identity/ui/cfg_identities_wnd.c
+++ b/src/windows/identity/ui/cfg_identities_wnd.c
@@ -230,6 +230,8 @@ handle_cfg_notify(HWND hwnd,
     HWND hw;
 
     node = get_window_node(hwnd);
+    if (node == NULL)
+        return TRUE;
 
     if (HIWORD(wParam) == WMCFG_APPLY) {
 
@@ -255,6 +257,8 @@ handle_notify(HWND hwnd,
 
     lpnm = (LPNMHDR) lParam;
     node = get_window_node(hwnd);
+    if (node == NULL)
+        return FALSE;
 
     if (lpnm->idFrom == IDC_CFG_TAB) {
         switch(lpnm->code) {
@@ -864,11 +868,14 @@ khm_cfg_add_ident_proc(HWND hwnd,
 
         khui_cw_destroy_cred_blob(d->nc);
         PFREE(d);
+        SetWindowLongPtr(hwnd, DWLP_USER, 0);
         break;
 
     case KHUI_WM_NC_NOTIFY:
         d = (add_ident_data *)(LONG_PTR)
             GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            break;
 
         switch(HIWORD(wParam)) {
         case WMNC_ADD_CONTROL_ROW:
diff --git a/src/windows/identity/ui/cfg_notif_wnd.c b/src/windows/identity/ui/cfg_notif_wnd.c
index 91650adb8..846d41714 100644
--- a/src/windows/identity/ui/cfg_notif_wnd.c
+++ b/src/windows/identity/ui/cfg_notif_wnd.c
@@ -282,6 +282,8 @@ khm_cfg_notifications_proc(HWND hwnd,
 
     case WM_COMMAND: {
         d = (notif_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         if (HIWORD(wParam) == BN_CLICKED) {
             refresh_data(hwnd, d);
@@ -299,6 +301,9 @@ khm_cfg_notifications_proc(HWND hwnd,
 
     case WM_TIMER: {
         d = (notif_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
+
         KillTimer(hwnd, 1);
         check_for_modification(d);
 
@@ -309,6 +314,8 @@ khm_cfg_notifications_proc(HWND hwnd,
 
     case WM_DESTROY: {
         d = (notif_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         khui_tracker_kill_controls(&d->tc_renew);
         khui_tracker_kill_controls(&d->tc_warn1);
@@ -325,6 +332,8 @@ khm_cfg_notifications_proc(HWND hwnd,
 
     case KHUI_WM_CFG_NOTIFY: {
         d = (notif_data *) (DWORD_PTR) GetWindowLongPtr(hwnd, DWLP_USER);
+        if (d == NULL)
+            return FALSE;
 
         if (HIWORD(wParam) == WMCFG_APPLY) {
             write_params(d);
diff --git a/src/windows/identity/ui/cfg_plugins_wnd.c b/src/windows/identity/ui/cfg_plugins_wnd.c
index 6290d3703..92f1cc06b 100644
--- a/src/windows/identity/ui/cfg_plugins_wnd.c
+++ b/src/windows/identity/ui/cfg_plugins_wnd.c
@@ -371,6 +371,8 @@ khm_cfg_plugins_proc(HWND hwnd,
 
             d = (plugin_dlg_data *) (LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                return FALSE;
 
             if (wParam == IDC_CFG_PLUGINS &&
                 (lpnm = (LPNMHDR) lParam) &&
@@ -426,6 +428,8 @@ khm_cfg_plugins_proc(HWND hwnd,
 
             d = (plugin_dlg_data *) (LONG_PTR)
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                return FALSE;
 
             switch (wParam) {
             case MAKEWPARAM(IDC_CFG_ENABLE, BN_CLICKED):
@@ -627,6 +631,9 @@ khm_cfg_plugins_proc(HWND hwnd,
 #ifdef DEBUG
             assert(d);
 #endif
+            if (d == NULL)
+                return TRUE;
+
             for (i=0; i<d->n_info; i++) {
 #ifdef DEBUG
                 assert(d->info[i]);
@@ -637,6 +644,7 @@ khm_cfg_plugins_proc(HWND hwnd,
             }
 
             PFREE(d);
+            SetWindowLongPtr(hwnd, DWLP_USER, 0);
 
             khm_set_dialog_result(hwnd, 0);
         }
diff --git a/src/windows/identity/ui/configwnd.c b/src/windows/identity/ui/configwnd.c
index 49ebfe48e..14eeb15a1 100644
--- a/src/windows/identity/ui/configwnd.c
+++ b/src/windows/identity/ui/configwnd.c
@@ -142,6 +142,8 @@ cfgui_initialize_dialog(HWND hwnd) {
     HICON hicon;
 
     d = cfgui_get_wnd_data(hwnd);
+    if (d == NULL)
+        return;
 
     /* create and fill the image list for the treeview */
 
@@ -241,6 +243,8 @@ cfgui_uninitialize_dialog(HWND hwnd) {
     HWND hwtv;
 
     d = cfgui_get_wnd_data(hwnd);
+    if (d == NULL)
+        return;
 
     hwtv = GetDlgItem(hwnd, IDC_CFG_NODELIST);
 
@@ -298,6 +302,9 @@ cfgui_activate_node(HWND hwnd, khui_config_node node) {
     HWND hwtv;
 
     d = cfgui_get_wnd_data(hwnd);
+    if (d == NULL)
+        return;
+
     hwtv = GetDlgItem(hwnd, IDC_CFG_NODELIST);
     hItem = (HTREEITEM) khui_cfg_get_param(node);
 
@@ -636,6 +643,9 @@ cfgui_update_state(HWND hwnd,
     int idx;
 
     d = cfgui_get_wnd_data(hwnd);
+    if (d == NULL)
+        return;
+
     hwtv = GetDlgItem(hwnd, IDC_CFG_NODELIST);
     hItem = (HTREEITEM) khui_cfg_get_param(node);
 
@@ -679,6 +689,9 @@ cfgui_dlgproc_generic(HWND hwnd,
 
     case WM_CTLCOLORSTATIC:
         d = cfgui_get_wnd_data(hwnd);
+        if (d == NULL)
+            break;
+
         return (BOOL)(DWORD_PTR) d->hbr_white;
 
     case WM_ERASEBKGND:
@@ -689,6 +702,8 @@ cfgui_dlgproc_generic(HWND hwnd,
             RECT r_fill;
 
             d = cfgui_get_wnd_data(hwnd);
+            if (d == NULL)
+                break;
 
             GetClientRect(hwnd, &r_client);
             SetRectEmpty(&r_logo);
@@ -781,6 +796,9 @@ cfgui_dlgproc(HWND hwnd,
         cfgui_uninitialize_dialog(hwnd);
 
         d = cfgui_get_wnd_data(hwnd);
+        if (d == NULL)
+            break;
+
         khui_delete_bitmap(&d->kbmp_logo);
         DeleteObject(d->hbr_white);
 
@@ -842,6 +860,9 @@ cfgui_dlgproc(HWND hwnd,
     case WM_CTLCOLORSTATIC:
         {
             d = cfgui_get_wnd_data(hwnd);
+            if (d == NULL)
+                break;
+
             return (BOOL)(DWORD_PTR) d->hbr_white;
         }
         /* implicit break */
@@ -878,6 +899,9 @@ cfgui_dlgproc(HWND hwnd,
 
         case WMCFG_SYNC_NODE_LIST:
             d = cfgui_get_wnd_data(hwnd);
+            if (d == NULL)
+                break;
+
             cfgui_sync_node_list(d, hwnd);
             break;
         }
diff --git a/src/windows/identity/ui/credwnd.c b/src/windows/identity/ui/credwnd.c
index 50e6c4efc..b2a7a1f0b 100644
--- a/src/windows/identity/ui/credwnd.c
+++ b/src/windows/identity/ui/credwnd.c
@@ -1127,14 +1127,17 @@ cw_timer_proc(HWND hwnd,
     KillTimer(hwnd, idEvent);
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
-    r = (khui_credwnd_row *) idEvent;
-    r->flags &= ~KHUI_CW_ROW_TIMERSET;
+    if (tbl == NULL)
+        return;
 
+    r = (khui_credwnd_row *) idEvent;
     nr = (int)(r - tbl->rows);
 
     if(nr < 0 || nr >= tbl->n_rows)
         return;
 
+    r->flags &= ~KHUI_CW_ROW_TIMERSET;
+
     if(r->flags & KHUI_CW_ROW_CRED) {
 
         nflags = cw_get_buf_exp_flags(tbl, (khm_handle) r->data);
@@ -3024,11 +3027,14 @@ cw_wm_destroy(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
 
-    cw_save_view(tbl, NULL);
+    if (tbl) {
+        cw_save_view(tbl, NULL);
 
-    cw_unload_view(tbl);
+        cw_unload_view(tbl);
 
-    PFREE(tbl);
+        PFREE(tbl);
+        SetWindowLongPtr(hwnd, 0, 0);
+    }
     return DefWindowProc(hwnd, uMsg, wParam, lParam);
 }
 
@@ -3051,6 +3057,8 @@ cw_wm_paint(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     BOOL has_dc = FALSE;
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        goto _exit;
 
     if (wParam != 0) {
         /* we assume that if wParam != 0, then that contains a device
@@ -3311,20 +3319,20 @@ cw_wm_size(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     khui_credwnd_tbl * tbl;
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl) {
+        cw_update_extents(tbl, TRUE);
 
-    cw_update_extents(tbl, TRUE);
-
-    GetClientRect(hwnd, &rect);
+        GetClientRect(hwnd, &rect);
 
-    if(tbl->hwnd_notif) {
-        SetWindowPos(
-            tbl->hwnd_notif,
-            tbl->hwnd_header,
-            rect.left,
-            tbl->header_height,
-            rect.right - rect.left,
-            tbl->cell_height * 4,
-            0);
+        if(tbl->hwnd_notif) {
+            SetWindowPos(tbl->hwnd_notif,
+                         tbl->hwnd_header,
+                         rect.left,
+                         tbl->header_height,
+                         rect.right - rect.left,
+                         tbl->cell_height * 4,
+                         0);
+        }
     }
     return DefWindowProc(hwnd, uMsg, wParam, lParam);
 }
@@ -3335,6 +3343,9 @@ cw_wm_notify(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     khui_credwnd_tbl * tbl;
     LPNMHDR pnmh;
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
+
     pnmh = (LPNMHDR) lParam;
     if(pnmh->hwndFrom == tbl->hwnd_header) {
         LPNMHEADER ph;
@@ -3361,6 +3372,9 @@ cw_kmq_wm_dispatch(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 
     kmq_wm_begin(lParam, &m);
 
+    if (tbl == NULL)
+        goto _skip_message;
+
     if(m->type == KMSG_CRED) {
         switch (m->subtype) {
         case KMSG_CRED_ROOTDELTA:
@@ -3573,6 +3587,8 @@ cw_kmq_wm_dispatch(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
         ;
     }
 
+ _skip_message:
+
     return kmq_wm_end(m, rv);
 }
 
@@ -4027,6 +4043,8 @@ cw_wm_mouse(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     int nm_state,nm_row,nm_col;
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
 
     /* we are basically trying to capture events where the mouse is
        hovering over one of the 'hotspots'.  There are two kinds of
@@ -4276,6 +4294,9 @@ cw_wm_hscroll(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     int newpos;
 
     tbl = (khui_credwnd_tbl *) (LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
+
     GetClientRect(hwnd, &cr);
     dx = tbl->scr_left;
 
@@ -4437,6 +4458,8 @@ cw_wm_vscroll(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     RECT cr;
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
 
     GetClientRect(hwnd, &cr);
     cr.top += tbl->header_height;
@@ -4567,6 +4590,8 @@ cw_pp_ident_proc(HWND hwnd,
     case WM_COMMAND:
         s = (khui_property_sheet *) (LONG_PTR) 
             GetWindowLongPtr(hwnd, DWLP_USER);
+        if (s == NULL)
+            return 0;
 
         switch(wParam) {
         case MAKEWPARAM(IDC_PP_IDDEF, BN_CLICKED):
@@ -4625,6 +4650,8 @@ cw_pp_ident_proc(HWND hwnd,
             lpp = (LPPSHNOTIFY) lParam;
             s = (khui_property_sheet *) (LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (s == NULL)
+                return 0;
 
             switch(lpp->hdr.code) {
             case PSN_APPLY:
@@ -4794,6 +4821,8 @@ cw_properties(HWND hwnd)
 
     khui_context_get(&ctx);
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
 
     if(ctx.scope == KHUI_SCOPE_NONE) {
         khui_context_release(&ctx);
@@ -4946,6 +4975,8 @@ cw_wm_command(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     khui_credwnd_tbl * tbl;
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
 
     if(HIWORD(wParam) == BN_CLICKED && 
        LOWORD(wParam) == KHUI_HTWND_CTLID) {
@@ -5303,6 +5334,8 @@ cw_wm_contextmenu(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     khui_credwnd_tbl * tbl;
 
     tbl = (khui_credwnd_tbl *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (tbl == NULL)
+        return 0;
 
     GetWindowRect(hwnd, &r);
 
diff --git a/src/windows/identity/ui/htwnd.c b/src/windows/identity/ui/htwnd.c
index a65ceceee..0f951a4ae 100644
--- a/src/windows/identity/ui/htwnd.c
+++ b/src/windows/identity/ui/htwnd.c
@@ -642,6 +642,8 @@ static LRESULT htw_paint(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
     int ext_height = 0;
 
     d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+    if (d == NULL)
+        return 0;
 
     if(!GetUpdateRect(hwnd, &r, !(d->flags & KHUI_HTWND_TRANSPARENT)))
         return 0;
@@ -945,6 +947,9 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             BOOL rv;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                return 0;
+
             newtext = (wchar_t *) lParam;
 
             if(d->text) {
@@ -978,21 +983,24 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             int i;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
-            if(d->text)
-                PFREE(d->text);
-            d->text = 0;
-
-            if(d->links) {
-                for(i=0;i<d->max_links;i++) {
-                    if(d->links[i])
-                        PFREE(d->links[i]);
+            if (d) {
+                if(d->text)
+                    PFREE(d->text);
+                d->text = 0;
+
+                if(d->links) {
+                    for(i=0;i<d->max_links;i++) {
+                        if(d->links[i])
+                            PFREE(d->links[i]);
+                    }
+                    PFREE(d->links);
                 }
-                PFREE(d->links);
-            }
 
-            clear_styles(d);
+                clear_styles(d);
 
-            PFREE(d);
+                PFREE(d);
+                SetWindowLongPtr(hwnd, 0, 0);
+            }
         }
         break;
 
@@ -1004,6 +1012,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             RECT r;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                return FALSE;
 
             GetClientRect(hwnd, &r);
             hbr = GetSysColorBrush(COLOR_WINDOW);
@@ -1040,6 +1050,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
                 break;
                 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
 
             if(d->active_link >= 0) {
                 SetCursor(d->hc_hand);
@@ -1053,6 +1065,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             khui_htwnd_data * d;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
 
             d->flags |= KHUI_HTWND_FOCUS;
 
@@ -1065,6 +1079,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             khui_htwnd_data * d;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
 
             d->flags &= ~KHUI_HTWND_FOCUS;
 
@@ -1077,6 +1093,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             khui_htwnd_data * d;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
 
             d->md_link = d->active_link;
 
@@ -1089,6 +1107,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             khui_htwnd_data * d;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
 
             if(d->md_link == d->active_link && d->md_link >= 0) {
                 /* clicked */
@@ -1109,6 +1129,8 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             RECT r;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
 
             old_pos = new_pos = d->scroll_left;
             ext = d->ext_width;
@@ -1194,6 +1216,9 @@ LRESULT CALLBACK khui_htwnd_proc(HWND hwnd,
             int nl;
 
             d = (khui_htwnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+            if (d == NULL)
+                break;
+
             p.x = GET_X_LPARAM(lParam) + d->scroll_left;
             p.y = GET_Y_LPARAM(lParam) + d->scroll_top;
                 
diff --git a/src/windows/identity/ui/newcredwnd.c b/src/windows/identity/ui/newcredwnd.c
index 6c8ea6094..e4797d7e8 100644
--- a/src/windows/identity/ui/newcredwnd.c
+++ b/src/windows/identity/ui/newcredwnd.c
@@ -93,6 +93,8 @@ nc_common_dlg_proc(HWND hwnd,
             khui_nc_wnd_data * d;
             d = (khui_nc_wnd_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, DWLP_USER);
+            if (d == NULL)
+                break;
 
             /* message sent by parent to notify us of something */
             switch(HIWORD(wParam)) {
@@ -1684,6 +1686,8 @@ nc_handle_wm_destroy(HWND hwnd,
     khm_del_dialog(hwnd);
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return TRUE;
 
     d->nc->ident_cb(d->nc, WMNC_IDENT_EXIT, NULL, 0, 0, 0);
 
@@ -1701,6 +1705,7 @@ nc_handle_wm_destroy(HWND hwnd,
     d->dlg_main = NULL;
 
     PFREE(d);
+    SetWindowLongPtr(hwnd, CW_PARAM, 0);
 
     return TRUE;
 }
@@ -1714,6 +1719,8 @@ nc_handle_wm_command(HWND hwnd,
     khui_nc_wnd_data * d;
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return 0;
 
     switch(HIWORD(wParam)) {
     case BN_CLICKED:
@@ -1885,6 +1892,8 @@ static LRESULT nc_handle_wm_moving(HWND hwnd,
     khui_nc_wnd_data * d;
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return FALSE;
 
     nc_notify_types(d->nc, KHUI_WM_NC_NOTIFY, 
                     MAKEWPARAM(0, WMNC_DIALOG_MOVE), (LPARAM) d->nc, TRUE);
@@ -1901,6 +1910,8 @@ static LRESULT nc_handle_wm_nc_notify(HWND hwnd,
     int id;
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return FALSE;
 
     switch(HIWORD(wParam)) {
 
@@ -2587,6 +2598,8 @@ static LRESULT nc_handle_wm_timer(HWND hwnd,
     khui_nc_wnd_data * d;
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return FALSE;
 
     if (wParam == NC_TIMER_SIZER) {
 
@@ -2702,6 +2715,9 @@ static LRESULT nc_handle_wm_notify(HWND hwnd,
     khui_nc_wnd_data * d;
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return FALSE;
+
     nmhdr = (LPNMHDR) lParam;
 
     if (nmhdr->code == TCN_SELCHANGE) {
@@ -2752,6 +2768,8 @@ static LRESULT nc_handle_wm_help(HWND hwnd,
     khui_nc_wnd_data * d;
 
     d = (khui_nc_wnd_data *)(LONG_PTR) GetWindowLongPtr(hwnd, CW_PARAM);
+    if (d == NULL)
+        return FALSE;
 
     hlp = (HELPINFO *) lParam;
 
diff --git a/src/windows/identity/ui/notifier.c b/src/windows/identity/ui/notifier.c
index afc774912..f1df06992 100644
--- a/src/windows/identity/ui/notifier.c
+++ b/src/windows/identity/ui/notifier.c
@@ -2356,7 +2356,10 @@ alerter_wnd_proc(HWND hwnd,
             d = (alerter_wnd_data *)(LONG_PTR) 
                 GetWindowLongPtr(hwnd, NTF_PARAM);
 
-            destroy_alerter_wnd_data(d);
+            if (d) {
+                destroy_alerter_wnd_data(d);
+                SetWindowLongPtr(hwnd, NTF_PARAM, 0);
+            }
 
             return TRUE;
         }
@@ -2446,6 +2449,8 @@ alert_bin_wnd_proc(HWND hwnd,
 #ifdef DEBUG
             assert(d);
 #endif
+            if (d == NULL)
+                break;
 
             if (in_printclient) {
                 hdc = (HDC) wParam;
@@ -2745,6 +2750,7 @@ alert_bin_wnd_proc(HWND hwnd,
     case WM_DESTROY:
         {
             /* nothing needs to be done here */
+            SetWindowLongPtr(hwnd, GWLP_USERDATA, 0);
         }
         return 0;
     }
diff --git a/src/windows/identity/ui/propertywnd.c b/src/windows/identity/ui/propertywnd.c
index 4255b481b..340684889 100644
--- a/src/windows/identity/ui/propertywnd.c
+++ b/src/windows/identity/ui/propertywnd.c
@@ -187,6 +187,9 @@ LRESULT CALLBACK khui_property_wnd_proc(
         case PW_WM_SET_RECORD:
             {
                 child = (pw_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
+                if (child == NULL)
+                    break;
+
                 kcdb_buf_release(child->record);
                 child->record = (khm_handle) lParam;
                 kcdb_buf_hold(child->record);
@@ -197,8 +200,11 @@ LRESULT CALLBACK khui_property_wnd_proc(
         case WM_DESTROY:
             {
                 child = (pw_data *)(LONG_PTR) GetWindowLongPtr(hwnd, 0);
-                kcdb_buf_release(child->record);
-                PFREE(child);
+                if (child) {
+                    kcdb_buf_release(child->record);
+                    PFREE(child);
+                    SetWindowLongPtr(hwnd, 0, 0);
+                }
             }
             break;
 
diff --git a/src/windows/identity/uilib/configui.c b/src/windows/identity/uilib/configui.c
index f2994d840..6f4f940a8 100644
--- a/src/windows/identity/uilib/configui.c
+++ b/src/windows/identity/uilib/configui.c
@@ -1081,6 +1081,7 @@ khui_cfg_free_dialog_data(HWND hwnd_dlg) {
 
     if (d) {
         PFREE(d);
+        SetWindowLongPtr(hwnd_dlg, DWLP_USER, 0);
     }
 
     return (d)?KHM_ERROR_SUCCESS: KHM_ERROR_NOT_FOUND;