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, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 33A94C32771 for ; Mon, 6 Jan 2020 06:55:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E68D521775 for ; Mon, 6 Jan 2020 06:55:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="rbiZz4bf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726477AbgAFGzH (ORCPT ); Mon, 6 Jan 2020 01:55:07 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:33016 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726391AbgAFGzH (ORCPT ); Mon, 6 Jan 2020 01:55:07 -0500 Received: by mail-pg1-f195.google.com with SMTP id 6so26436634pgk.0 for ; Sun, 05 Jan 2020 22:55:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=kMjWw4ObQXa5tU7/4BC/Kf0fTl6f93HTAnRhQj6fbYQ=; b=rbiZz4bfFgf1jTPa3LFYJTALJqVunQJkyqIBz6qTTRJ6IXYmBRVMVnbtv89C27cCMK GbnyT86UTVdO5nGt2TPC3Yd7V5jLEErJRNJKZa9DG/UBSMW3BqhhyY78sxr0Mogby9cO EMZ2mEw5bnYmr8GbTYEPl5KDiQOfgOBdoLrsZOrDrM4rIpIRlxcDX1uLdxRCId7WIQle UGdj1rzTvzVdEwVSNUy8QcUmnfLjoBUZ0q5fo4bfYF/JhyVJR8Qi37DnKQCifiytQ7gI L7L1jnfWUoEIkd1cmkhZM1QLeVS7IWAcn218pivk4ZSk4LyFAefJe1aMUFfiGWRtlXOr 1ebw== 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=kMjWw4ObQXa5tU7/4BC/Kf0fTl6f93HTAnRhQj6fbYQ=; b=U8KzMKsXUaB6fSAXl/rbxn6RhU5l/rIE63wu3cmyHUOt47oBECAN0KvqOS5G0V+UC/ 0YW5Duq1K2bDxvSiFRVjC6mR4mRS1+sEGkcozt5kbZfT2BXbT+fo56qjbXh0YtQI4OAS yeWXBB8wGahuRMlfeaYc7uX8QvYyAGMMsQfqowFm6KwPy1ZnJd2zIXKEmt6guqxi75Ar Tz113ILACGEUKK6KtZ4AGGAi8DIHHcYfYeMLeciZG58uQuAB6+8/uB/+Dd12HpUH3DLw zFjaVLRvRe3OCxblCBe0m8t/3ExxYjRdSAHkAdP/Gv02LDLX8kabZ0ZYD571IiSLjk0G 8gMw== X-Gm-Message-State: APjAAAVyQVfPuc0h3r+o+2nUW0Yykqk3kHV5Um/pZzXAOULGBO8FeL84 qRBKrjl0/flCvhBbWJJ+PnwWwA== X-Google-Smtp-Source: APXvYqzDrb4T5b5fxDDS/CxIRlUlD59ItmCXmCwsdQJKzsrikz4XhCQmY7mMb4+ZrEIymAreV3RhQA== X-Received: by 2002:a65:56c9:: with SMTP id w9mr105330256pgs.296.1578293705329; Sun, 05 Jan 2020 22:55:05 -0800 (PST) Received: from localhost ([122.172.26.121]) by smtp.gmail.com with ESMTPSA id l8sm22852583pjy.24.2020.01.05.22.55.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 05 Jan 2020 22:55:04 -0800 (PST) Date: Mon, 6 Jan 2020 12:25:02 +0530 From: Viresh Kumar To: chenqiwu 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: <20200106065502.bimpddvrvmfm2f5f@vireshk-i7> References: <1577515439-14477-1-git-send-email-qiwuchen55@gmail.com> <20200106054811.uduf2qdn5ecvbwrc@vireshk-i7> <20200106065249.GA16392@cqw-OptiPlex-7050> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200106065249.GA16392@cqw-OptiPlex-7050> User-Agent: NeoMutt/20180716-391-311a52 Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On 06-01-20, 14:52, chenqiwu wrote: > 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. The second one is better as it doesn't make copy of the policy, but rather just increments the counter. > 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. I think there are enough locks in place to avoid such issues and they shouldn't happen. > > > + 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 -- viresh