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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 1C817C32771 for ; Mon, 6 Jan 2020 06:52:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA7E821775 for ; Mon, 6 Jan 2020 06:52:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="TxRMT6Eu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726391AbgAFGwx (ORCPT ); Mon, 6 Jan 2020 01:52:53 -0500 Received: from mail-pj1-f66.google.com ([209.85.216.66]:52435 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726294AbgAFGwx (ORCPT ); Mon, 6 Jan 2020 01:52:53 -0500 Received: by mail-pj1-f66.google.com with SMTP id a6so7185893pjh.2; Sun, 05 Jan 2020 22:52:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=ILbtPQ49UQ5/z2fgV/Pv/NXVgfndSPVO/Z+iSzamE50=; b=TxRMT6EuVhwzU6EmNtGY1bRoMPFMdfiDhDdKhwErLKT61PVaGUf4J9+nhf4SPZTADG 91+cf6E/ra/fgI7GUqbL2FSkkK1FnEnSP3nLEymeIwXACeq9bWBckwbrmab6uvLr3naJ XuQofEyR7tJUvoIM+tbNih5jv8iCnufHolp2GKt6CfWbLgL249AA1EFlsq27lDGTOxnx t7NqStB9h6OpMKiEkvSEYpKQRbi4NWZ/di/nETGVQGtQkD2OkTuRWCz/YGXP8QfanuHM 84CnMFIhKMo+lmf8Y6D/Jy+OApz9Bkt980yDikVxbW3Zs+L4jZuIoVNfZ1Vvlmnd/1jk fO1w== 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=ILbtPQ49UQ5/z2fgV/Pv/NXVgfndSPVO/Z+iSzamE50=; b=Ky2ZWvsY4CUZN3KtzBUZZaedvvqiIRMxA0xyoiPesOQJ2/nbb2H4ttGw1yBaiboPXm KuSb/BRdnyv6Ln8TtYpB18KmGVkbib6O1+GtWL/BGfxs2A0fzcHq4i7pObca9ZnGduDs sLl1EUR4NB0mnFYlzm6Vq/AjfCshXFcaFPxKQtCZa1bOXoUl2A2rkhYQlPtT09tK3W2U cb9AqX8ysunKAiYb7QE1cmxn1qdJbZ0pB3yMRulqaxMvKJDlJ0ZOkrje6S/ypGev0sbr GXez0Qzg3BqTRNtOdOkfk99Uo+q8m+dbCWNWJLFV9R5r9SBrOgNcKUByFVjL7Hc80y52 Ylmg== X-Gm-Message-State: APjAAAXuS5yzUNbVuzr5qdKAq3nmCqaej8uqoO5tmxhyS8BjWLgn8PC/ NivWT8MrQ361tQCYt4N8tfrFyoY578k= X-Google-Smtp-Source: APXvYqwOS+lopbhTJeonZU5znewHDoRirY65GOzExc1QuBLtvUvMa4G2mxAEaK1WabMcrppIQ6uaoA== X-Received: by 2002:a17:90a:8a8f:: with SMTP id x15mr42050937pjn.87.1578293572889; Sun, 05 Jan 2020 22:52:52 -0800 (PST) Received: from localhost ([43.224.245.179]) by smtp.gmail.com with ESMTPSA id q199sm77129113pfq.163.2020.01.05.22.52.51 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Sun, 05 Jan 2020 22:52:52 -0800 (PST) Date: Mon, 6 Jan 2020 14:52:49 +0800 From: chenqiwu To: Viresh Kumar Cc: kgene@kernel.org, krzk@kernel.org, rjw@rjwysocki.net, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH] cpufreq: s3c: avoid use after free issue in xxx_cpufreq_reboot_notifier_evt() Message-ID: <20200106065249.GA16392@cqw-OptiPlex-7050> References: <1577515439-14477-1-git-send-email-qiwuchen55@gmail.com> <20200106054811.uduf2qdn5ecvbwrc@vireshk-i7> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200106054811.uduf2qdn5ecvbwrc@vireshk-i7> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On Mon, Jan 06, 2020 at 11:18:11AM +0530, Viresh Kumar wrote: > On 28-12-19, 14:43, qiwuchen55@gmail.com wrote: > > From: chenqiwu > > > > There is a potential UAF issue in xxx_cpufreq_reboot_notifier_evt() that > > the cpufreq policy of cpu0 has been released before using it. So we should > > make a judgement to avoid it. > > There is no UAF problem here, but that we do cpufreq_cpu_get() with a > corresponding cpufreq_cpu_put(). > > > Signed-off-by: chenqiwu > > --- > > drivers/cpufreq/s3c2416-cpufreq.c | 11 ++++++++++- > > drivers/cpufreq/s5pv210-cpufreq.c | 10 +++++++++- > > 2 files changed, 19 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/cpufreq/s3c2416-cpufreq.c b/drivers/cpufreq/s3c2416-cpufreq.c > > index 1069103..0f576ba 100644 > > --- a/drivers/cpufreq/s3c2416-cpufreq.c > > +++ b/drivers/cpufreq/s3c2416-cpufreq.c > > @@ -304,6 +304,7 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this, > > { > > struct s3c2416_data *s3c_freq = &s3c2416_cpufreq; > > int ret; > > + struct cpufreq_policy policy; > > > > mutex_lock(&cpufreq_lock); > > > > @@ -318,7 +319,15 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this, > > */ > > if (s3c_freq->is_dvs) { > > pr_debug("cpufreq: leave dvs on reboot\n"); > > - ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0); > > + > > + memset(&policy, 0, sizeof(policy)); > > + ret = cpufreq_get_policy(&policy, 0); > > + if (ret < 0) { > > + pr_debug("cpufreq: get no policy for cpu0\n"); > > + return NOTIFY_BAD; > > + } > > + > > This doesn't make sense to me, why don't you do cpufreq_cpu_get() and > put() instead ? > Hi viresh, I can't explain which approach is better, but I think both approaches are effective for the situation. By the way, there is a possibility that the cpu0 hotplug thread will call cpufreq_policy_free() to free cpufreq policy if cpu0 hotplug failed. I think there should be a judgement to avoid this UAF risk if necessary, or we just do panic if cpu0's cpufreq policy is free. > > + ret = cpufreq_driver_target(&policy, FREQ_SLEEP, 0); > > if (ret < 0) > > return NOTIFY_BAD; > > } > > diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c > > index 5d10030..d99b4b1 100644 > > --- a/drivers/cpufreq/s5pv210-cpufreq.c > > +++ b/drivers/cpufreq/s5pv210-cpufreq.c > > @@ -555,8 +555,16 @@ static int s5pv210_cpufreq_reboot_notifier_event(struct notifier_block *this, > > unsigned long event, void *ptr) > > { > > int ret; > > + struct cpufreq_policy *policy; > > > > - ret = cpufreq_driver_target(cpufreq_cpu_get(0), SLEEP_FREQ, 0); > > + policy = cpufreq_cpu_get(0); > > + if (!policy) { > > + pr_debug("cpufreq: get no policy for cpu0\n"); > > + return NOTIFY_BAD; > > + } > > + > > + ret = cpufreq_driver_target(policy, SLEEP_FREQ, 0); > > + cpufreq_cpu_put(policy); > > Like what is done here. > > Also add a blank line here. > > > if (ret < 0) > > return NOTIFY_BAD; > > > > -- > > 1.9.1 > > -- > viresh Thanks for your review! Qiwu