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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 E9DADC433FF for ; Mon, 29 Jul 2019 06:56:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEA732073F for ; Mon, 29 Jul 2019 06:56:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=resnulli-us.20150623.gappssmtp.com header.i=@resnulli-us.20150623.gappssmtp.com header.b="pPD/sBPW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727000AbfG2G46 (ORCPT ); Mon, 29 Jul 2019 02:56:58 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:38603 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726767AbfG2G44 (ORCPT ); Mon, 29 Jul 2019 02:56:56 -0400 Received: by mail-wr1-f65.google.com with SMTP id g17so60496983wrr.5 for ; Sun, 28 Jul 2019 23:56:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=resnulli-us.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=77kBMlKTAenEQAkiXPo05Wm16zYsJQ8LVBsU59Q9oVA=; b=pPD/sBPWrxLVysfk2Ps6tNucGWwJlCOr6XR//BG7RR8oyJv9v2k0wFNw+aXtAtsXYm luzVZfhEqo8WA7WT/fSQnZtLwComZEEyj8mBmG+fymQinBJIgbaFF7evSjaTfz2+9Jol 2kUHUh75XX13bm33it4tEGzQXVUJxh83BJ/xYgTjF4zu0Ddf23BiggfphU3EaRAJctJM Bh+an0KVkI7Z0NnC+O2OUljKfZ26Iq8iDoRE6D8JEdsKtNDEeVU2Mh0cLcsxyhaZW5SH 2HmMkqHzIIN65y/5FRFy5MVWQsGTiAc5O+XD9DHQPA+sFP7xWlzl0Jkw0UevTMw/Mxm0 fX9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=77kBMlKTAenEQAkiXPo05Wm16zYsJQ8LVBsU59Q9oVA=; b=QLsQDSj2nKaVBs+6BkA5Aj9HsgaDNcJVvGHN29G0azM6UHrDrk1f88OK2ClYvpXTyT f1HFfo/n4WqoGOgSL7b0f+LtJVFvz0OZhCeV8yl+8OgmND0jbQqEzyMQrAOCRQHEiaEm SuQjcSQ0rTrayubPi+buHkP/5MJRiZ56duKs0CGXyc+k6VYntcfzUywqd0PGKt9Xza/A phmwbqLLBaZ8aam4Ri6gCGCMpsGBvMAbBJYd4YrXx//gMPb7+OIniJ7MVJGJcYkAdfQW pJlwW74Q4UssFoMLCKuwTeELyifgySumrRu7ed7kKdnkb0/h6iXoj+j1TQTxcx54RVvl ygVg== X-Gm-Message-State: APjAAAXPmBYKRbuOmoCmA+t9Wfqk038Huq+sEq9pm9MqiPzD+6jUNCJ2 /E6lE0AO60yrZu+2FHd7OfE= X-Google-Smtp-Source: APXvYqwltHE9iEWxKnbbh87k8UY3j+nd3lsQOuNtcbriLQ+0SNoXQVr2iH8MQnAoJMCtZAHoz6/ZDg== X-Received: by 2002:adf:fd08:: with SMTP id e8mr122286409wrr.147.1564383414116; Sun, 28 Jul 2019 23:56:54 -0700 (PDT) Received: from localhost (mail.chocen-mesto.cz. [85.163.43.2]) by smtp.gmail.com with ESMTPSA id e7sm54869909wmd.0.2019.07.28.23.56.53 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sun, 28 Jul 2019 23:56:53 -0700 (PDT) Date: Mon, 29 Jul 2019 08:56:53 +0200 From: Jiri Pirko To: Jia-Ju Bai Cc: jhs@mojatatu.com, xiyou.wangcong@gmail.com, davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: sched: Fix a possible null-pointer dereference in dequeue_func() Message-ID: <20190729065653.GA2211@nanopsycho> References: <20190729022157.18090-1-baijiaju1990@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190729022157.18090-1-baijiaju1990@gmail.com> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mon, Jul 29, 2019 at 04:21:57AM CEST, baijiaju1990@gmail.com wrote: >In dequeue_func(), there is an if statement on line 74 to check whether >skb is NULL: > if (skb) > >When skb is NULL, it is used on line 77: > prefetch(&skb->end); > >Thus, a possible null-pointer dereference may occur. > >To fix this bug, skb->end is used when skb is not NULL. > >This bug is found by a static analysis tool STCheck written by us. > >Signed-off-by: Jia-Ju Bai Fixes tag, please? >--- > net/sched/sch_codel.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > >diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c >index 25ef172c23df..30169b3adbbb 100644 >--- a/net/sched/sch_codel.c >+++ b/net/sched/sch_codel.c >@@ -71,10 +71,10 @@ static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx) > struct Qdisc *sch = ctx; > struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); > >- if (skb) >+ if (skb) { > sch->qstats.backlog -= qdisc_pkt_len(skb); >- >- prefetch(&skb->end); /* we'll need skb_shinfo() */ >+ prefetch(&skb->end); /* we'll need skb_shinfo() */ >+ } > return skb; > } > >-- >2.17.0 >