From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F30E0C3A59F for ; Fri, 30 Aug 2019 00:07:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C110B2173E for ; Fri, 30 Aug 2019 00:07:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726670AbfH3AHv (ORCPT ); Thu, 29 Aug 2019 20:07:51 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:55646 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726014AbfH3AHv (ORCPT ); Thu, 29 Aug 2019 20:07:51 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id EAB7E153C9A48; Thu, 29 Aug 2019 17:07:48 -0700 (PDT) Date: Thu, 29 Aug 2019 17:07:48 -0700 (PDT) Message-Id: <20190829.170748.656667843147010952.davem@davemloft.net> To: olteanv@gmail.com Cc: jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, vinicius.gomes@intel.com, vedang.patel@intel.com, leandro.maciel.dorileo@intel.com, netdev@vger.kernel.org Subject: Re: [PATCH net 1/3] taprio: Fix kernel panic in taprio_destroy From: David Miller In-Reply-To: <20190828144829.32570-2-olteanv@gmail.com> References: <20190828144829.32570-1-olteanv@gmail.com> <20190828144829.32570-2-olteanv@gmail.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Thu, 29 Aug 2019 17:07:49 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Vladimir Oltean Date: Wed, 28 Aug 2019 17:48:27 +0300 > taprio_init may fail earlier than this line: > > list_add(&q->taprio_list, &taprio_list); > > i.e. due to the net device not being multi queue. > > Attempting to remove q from the global taprio_list when it is not part > of it will result in a kernel panic. > > Fix it by iterating through the list and removing it only if found. > > Signed-off-by: Vladimir Oltean I don't like this solution for two reaons, I think it's actually error prone, and now every taprio_destroy() eats the cost of traversing the entire list. The whole reason to use a list head is O(1) removal. Just init the list head early in the creation then the list_del() just works.