drivers/usb/class/cdc-acm.c: clear dangling pointer

On some failures, the country_code field of an acm structure is freed
without freeing the acm structure itself.  Elsewhere, operations including
memcpy and kfree are performed on the country_code field.  The patch sets
the country_code field to NULL when it is freed, and likewise sets the
country_code_size field to 0.
Signed-off-by: Julia Lawall <julia@diku.dk>
Acked-by: Oliver Neukum <oneukum@suse.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/cdc-acm.c

@@ -1230,6 +1230,8 @@ static int acm_probe(struct usb_interface *intf,
 		i = device_create_file(&intf->dev, &dev_attr_wCountryCodes);
 		if (i < 0) {
 			kfree(acm->country_codes);
+			acm->country_codes = NULL;
+			acm->country_code_size = 0;
 			goto skip_countries;
 		}
 
@@ -1238,6 +1240,8 @@ static int acm_probe(struct usb_interface *intf,
 		if (i < 0) {
 			device_remove_file(&intf->dev, &dev_attr_wCountryCodes);
 			kfree(acm->country_codes);
+			acm->country_codes = NULL;
+			acm->country_code_size = 0;
 			goto skip_countries;
 		}
 	}