From patchwork Sun Jan 5 12:50:50 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: chenqiwu X-Patchwork-Id: 11318231 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 17484138C for ; Sun, 5 Jan 2020 12:50:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE0E4207FD for ; Sun, 5 Jan 2020 12:50:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RxnpqQhv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725991AbgAEMu5 (ORCPT ); Sun, 5 Jan 2020 07:50:57 -0500 Received: from mail-pf1-f193.google.com ([209.85.210.193]:39870 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725990AbgAEMu5 (ORCPT ); Sun, 5 Jan 2020 07:50:57 -0500 Received: by mail-pf1-f193.google.com with SMTP id q10so25657536pfs.6 for ; Sun, 05 Jan 2020 04:50:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=O73F02mr1vEr7ShVhQ/rPt/DWjk1N7vtrWpN2HwbxPw=; b=RxnpqQhvQ5bv7z0xIAnD8gdhFyHKqKqpdXwTBhsUdEpg4sSugA+Vrg+Lmzf2NpnmLO k22F3pGksCJ5uQ+ueN0NIRXsZNOZuD1vRoDmkDrxuHiRk6/pl0MzljAmGMdmWfGPQFjF MZWdUkytwQeduUN8GEa4mwe+wZ2F3Krq2JVCeI+/Pyf/cuxId0btKL3aCfzLBsSwv1rp slF/9GvYZkEQ5yxavZwbu0zKrbowEHUqxJ4GsYFcAcxmKtp90yi1nke2ieHiW/Y7W8rs Pv0qHXykJtQjq3Ag0JxThiJ0f+3T4jeeYm2rTkdjGLbaIp/Z0LZ6y8p/qj/x0xjdFpBB QY8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=O73F02mr1vEr7ShVhQ/rPt/DWjk1N7vtrWpN2HwbxPw=; b=E3UvgFNvK+6BOo40nYuUikmmW0ZEsxfokChijKmNEmyMlHPd47sExMGrHbkSKauaqx 8kMwYRP8/rWF2VLg6tL/tRvKzT/Hj/jQBjo3ZLpziCR47z4/O9XsDEqKJlkSDEhe1mgI bHDlrLUC64P8T/7p9DR6WazvyvW23eMhCa2q0kjIKsfnnUSuhB3697ukXhAMJZLzX8Ye rq/koyP1IMv9yJomw01ANzjbjsnomdqF00LeuXzCax8Mxi1NtHJztGZRFe6jILWh97pA BVgL6JlBHoIf0DbQP1D+Y5/B3wy4MnuDCzrvlMN+aT61gEXV0avXY0qmYKeCTg19irab kWmA== X-Gm-Message-State: APjAAAXvH9DfqYOddhIpYVPyoLPih3C/34E/ihKw1Vjq6Afj5oFxtd4O crf4SIUWLgNQnE7XB4HluOE= X-Google-Smtp-Source: APXvYqxUgpmdlnIXGhbVIEYm+2ZG/SLeZ4ocWYD5rb0O++qhXkZAxHm0/oxmD2mMWohAObY+FG5NaQ== X-Received: by 2002:a62:e908:: with SMTP id j8mr93764073pfh.55.1578228656502; Sun, 05 Jan 2020 04:50:56 -0800 (PST) Received: from localhost ([43.224.245.179]) by smtp.gmail.com with ESMTPSA id z130sm70081453pgz.6.2020.01.05.04.50.55 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Sun, 05 Jan 2020 04:50:56 -0800 (PST) From: qiwuchen55@gmail.com To: mmayer@broadcom.com, rjw@rjwysocki.net, viresh.kumar@linaro.org, f.fainelli@gmail.com Cc: bcm-kernel-feedback-list@broadcom.com, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, chenqiwu Subject: [PATCH v2] cpufreq: brcmstb-avs-cpufreq: avoid potential stuck and UAF risk Date: Sun, 5 Jan 2020 20:50:50 +0800 Message-Id: <1578228650-17157-1-git-send-email-qiwuchen55@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: chenqiwu brcm_avs_cpufreq_get() calls cpufreq_cpu_get() to get cpufreq policy, meanwhile, it also increments the kobject reference count of policy to mark it busy. However, a corresponding call of cpufreq_cpu_put() is ignored to decrement the kobject reference count back, which may lead to a potential stuck risk that percpu cpuhp thread deadly waits for dropping of kobject refcount when percpu cpufreq policy free. The call trace of stuck risk could be: cpufreq_online() //If cpufreq online failed, goto out_free_policy. ->cpufreq_policy_free() //Do cpufreq_policy free. ->cpufreq_policy_put_kobj() ->kobject_put() //Skip if policy kfref count is not 1. ->cpufreq_sysfs_release() ->complete() //Complete policy->kobj_unregister. ->wait_for_completion() //Wait for policy->kobj_unregister. A simple way to avoid this stuck risk is use cpufreq_cpu_get_raw() instead of cpufreq_cpu_get(), since this can be easily exercised by attempting to force an unbind of the CPUfreq driver. Signed-off-by: chenqiwu --- drivers/cpufreq/brcmstb-avs-cpufreq.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c index 77b0e5d..6d2bf5c 100644 --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c @@ -452,8 +452,15 @@ static bool brcm_avs_is_firmware_loaded(struct private_data *priv) static unsigned int brcm_avs_cpufreq_get(unsigned int cpu) { - struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); - struct private_data *priv = policy->driver_data; + struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu); + struct private_data *priv; + + if (!policy) + return 0; + + priv = policy->driver_data; + if (!priv || !priv->base) + return 0; return brcm_avs_get_frequency(priv->base); }