staging: tidspbridge/pmgr: additional checking after return from strlen_user

  strlen_user will return the length including final NUL.
    and will return 0 if failed (for example: if user string not NUL terminated)

  so need check whether it is an invalid parameter.

addtional info:
  can reference the comments of strlen_user in lib/strnlen_user.c
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: Omar Ramirez Luna <omar.ramirez@copitl.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/tidspbridge/pmgr/dspapi.c

@@ -414,10 +414,13 @@ u32 mgrwrap_register_object(union trapped_args *args, void *pr_ctxt)
 	CP_FM_USR(&uuid_obj, args->args_mgr_registerobject.uuid_obj, status, 1);
 	if (status)
 		goto func_end;
-	/* path_size is increased by 1 to accommodate NULL */
 	path_size = strlen_user((char *)
-				args->args_mgr_registerobject.sz_path_name) +
-	    1;
+				args->args_mgr_registerobject.sz_path_name);
+	if (!path_size) {
+		status = -EINVAL;
+		goto func_end;
+	}
+
 	psz_path_name = kmalloc(path_size, GFP_KERNEL);
 	if (!psz_path_name) {
 		status = -ENOMEM;