[PATCH] dbus_new_handlers: Don't send NULL to dbus_message_new_error

[Dan Williams]

On Tue, 2010-10-05 at 12:07 -0700, Paul Stewart wrote:
> From: Paul Stewart <pstew at google.com>
> 
> The new DBus API helper function wpas_dbus_error_unknown_error
> function can be called as a result of a failure within internal
> getter calls, which will call this function with a NULL message
> parameter.  However, dbus_message_new_error looks very unkindly
> (i.e, abort()) on a NULL message, so in this case, we should not
> call it.
> 
> I've observed this course of events during a call to
> wpas_dbus_getter_bss_wpa with a faileld parse of the IE parameter.
> We got here through a call to fill_dict_with_properties which
> explicitly calls getters with a NULL message parameter.  Judging
> from the way it is called, this could easily occur if an AP sends
> out a malformed (or mis-received) probe response.  I usually run
> into this problem while driving through San Francisco, so I'm
> exposed to any number of base stations along this path.

I'm thinking that instead, we should just pass the DBusMessage down to
fill_dict_with_properties() so that they can do something intelligent
with the error.  That would probably  mean changing the return type of
fill_dict_with_properties() to a DBusMessage* which would be NULL on
success, and an error message on error.

Dan

> ---
>  wpa_supplicant/dbus/dbus_new_handlers.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
> 
> diff --git a/wpa_supplicant/dbus/dbus_new_handlers.c b/wpa_supplicant/dbus/dbus_new_handlers.c
> index 8e87e20..b9f6a8d 100644
> --- a/wpa_supplicant/dbus/dbus_new_handlers.c
> +++ b/wpa_supplicant/dbus/dbus_new_handlers.c
> @@ -117,6 +117,16 @@ static char * wpas_dbus_new_decompose_object_path(const char *path,
>  DBusMessage * wpas_dbus_error_unknown_error(DBusMessage *message,
>  					    const char *arg)
>  {
> +	/*
> +	 * This function can be called as a result of a failure
> +	 * within internal getter calls, which will call this function
> +	 * with a NULL message parameter.  However, dbus_message_new_error
> +	 * looks very unkindly (i.e, abort()) on a NULL message, so
> +	 * in this case, we should not call it.
> +	 */
> +	if (message == NULL)
> +		return NULL;
> +
>  	return dbus_message_new_error(message, WPAS_DBUS_ERROR_UNKNOWN_ERROR,
>  				      arg);
>  }