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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, FREEMAIL_REPLYTO_END_DIGIT,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 674D1C43441 for ; Thu, 29 Nov 2018 07:38:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 12B392081C for ; Thu, 29 Nov 2018 07:38:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="HBHiuNdy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 12B392081C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=163.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727560AbeK2Sma (ORCPT ); Thu, 29 Nov 2018 13:42:30 -0500 Received: from m12-15.163.com ([220.181.12.15]:42019 "EHLO m12-15.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726587AbeK2Sma (ORCPT ); Thu, 29 Nov 2018 13:42:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version; bh=Fva0u psThI9/5B/dKzbVzKIt0VO+FAZlovF3pRRZcnM=; b=HBHiuNdyJUPoiUhA3OTdO O0XntqpN5KEpBMRnggtSDIqKFfqNKpF1zI5J5TeAywt5XV3ouaQzh5xqYkgPYs28 g0+yEbmErE1DE+WXrcwJZ8cLRaBzJdgx8T+Z1ejTROSJ0PpU4CfXTdd20iZaIQ4q FbxTI30vfkOV6g3/gwPIxk= Received: from bp (unknown [106.120.213.96]) by smtp11 (Coremail) with SMTP id D8CowABniS1Rl_9b5izuAQ--.18628S2; Thu, 29 Nov 2018 15:37:53 +0800 (CST) Date: Thu, 29 Nov 2018 15:37:56 +0800 From: PanBian To: David Miller Cc: thomas.lendacky@amd.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] amd-xgbe: set skb to NULL after freeing it Message-ID: <20181129073756.GA73287@bp> Reply-To: PanBian References: <1543392585-17962-1-git-send-email-bianpan2016@163.com> <20181128.104931.1898736297454841540.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181128.104931.1898736297454841540.davem@davemloft.net> User-Agent: Mutt/1.5.24 (2015-08-30) X-CM-TRANSID: D8CowABniS1Rl_9b5izuAQ--.18628S2 X-Coremail-Antispam: 1Uf129KBjvdXoW7Wr4xGryxKrWxKr4fXFWDurg_yoWfXFb_Wr ykX3WkCw1DCasrGF4ftrWfXwn3Ga1UGry0qw48XrsFvr9xJrZ3C3ykWrnYgryxu392kF1U GFn5Za97uw13ujkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7IUntku7UUUUU== X-Originating-IP: [106.120.213.96] X-CM-SenderInfo: held01tdqsiiqw6rljoofrz/xtbBUREOclaD0WuU1QAAsS Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 28, 2018 at 10:49:31AM -0800, David Miller wrote: > From: Pan Bian > Date: Wed, 28 Nov 2018 16:09:45 +0800 > > If either of these two cases are executed, it means that it must be > the case that: > > !last || context_next > > is FALSE, therefore the conditional in the tail code of this function: > > /* Check if we need to save state before leaving */ > if (received && (!last || context_next)) { > rdata = XGBE_GET_DESC_DATA(ring, ring->cur); > rdata->state_saved = 1; > rdata->state.skb = skb; > rdata->state.len = len; > rdata->state.error = error; > } > > will not trigger, and therefore we will not record the free'd SKB. > > And if we iterate the loop again, it is guaranteed that 'skb' will > be set to a new packet or NULL. > > So there is no problem here. Got it. Sorry for my misunderstanding. Thank you and Tom for the detailed explanations. Pan