From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELufFpLy8gavHYEQLbT/YYbZLbXmywjtjL5DTRgNgON95yW5tNVSgwFOIkl30KrQjf1tunDo ARC-Seal: i=1; a=rsa-sha256; t=1521214732; cv=none; d=google.com; s=arc-20160816; b=FCg2ZvBtEuUBmbhWXUJwAIQ99iyAsg7Iu+LhswhrzySLctV+guEfBeBHD/EbYZhGPU zO4JXCe8t2ycA6Ltap0q4yhx0h4F0vNwtOwOJ1LajnG21JMCkpddftWKHPJzvalbJOma xVUiv9yFaPsgxA3USeugMNyPe6xTiplxOAVOAD/8qNxdflTAyh8zcXVgFukvpdsZDcrp PvNz4pNcF8At3nUg/fNCLEq/QV941kp4dZELDisdrxtLUNjKRxkKdCne4E3BXAr9lkL9 cys+7vS4wp5NlHeenTrgRkRuZE0D0v6Uz/c/bqM30HFgfSbU5fKXA8GhjMqTMTrOJ1rb +V5A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=giqgu/iJXNB9c0cqQyuN6TESnxTmcALblVCwc8f5LxY=; b=i2R4mE0b4PhxgoSgMFHJ4NFx2L5OBEmYbHp5w+jZr2gsZNMRnMAujmkpkBAnUMBqxY bnKWW81zgsNXltSkSX/UCyx+ErCXzn6MKtT563GO4QPoQa1opqfCoPyUkHHEJRnYNCK4 +Kth9rH6PqJkjMkK+wklyUItf5IuJNj2YVgGQnzPMQ+djnTpU1QnUvlyKhEvdf4f+qY6 Tm9yahzO+47HRyjWcX9D1eV1nkRR8tKXUfaruKVpkyWTFbD/TaQlV0ZNoZ6QZu+91H5G WSZdO0QYcI3Yo9IyVnXe2H3BJmN3OMx+gdUK2ZyR6o/SusBzIfoe4ofuoTBrU02qMVTZ llSA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Rafael J. Wysocki" , Viresh Kumar , Sasha Levin Subject: [PATCH 4.14 063/109] cpufreq: Fix governor module removal race Date: Fri, 16 Mar 2018 16:23:32 +0100 Message-Id: <20180316152333.395213939@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180316152329.844663293@linuxfoundation.org> References: <20180316152329.844663293@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1595109259104693147?= X-GMAIL-MSGID: =?utf-8?q?1595109259104693147?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Rafael J. Wysocki" [ Upstream commit a8b149d32b663c1a4105273295184b78f53d33cf ] It is possible to remove a cpufreq governor module after cpufreq_parse_governor() has returned success in store_scaling_governor() and before cpufreq_set_policy() acquires a reference to it, because the governor list is not protected during that period and nothing prevents the governor from being unregistered then. Prevent that from happening by acquiring an extra reference to the governor module temporarily in cpufreq_parse_governor(), under cpufreq_governor_mutex, and dropping it in store_scaling_governor(), when cpufreq_set_policy() returns. Note that the second cpufreq_parse_governor() call site is fine, because it only cares about the policy member of new_policy. Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/cpufreq/cpufreq.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -631,6 +631,8 @@ static int cpufreq_parse_governor(char * *governor = t; err = 0; } + if (t && !try_module_get(t->owner)) + t = NULL; mutex_unlock(&cpufreq_governor_mutex); } @@ -759,6 +761,10 @@ static ssize_t store_scaling_governor(st return -EINVAL; ret = cpufreq_set_policy(policy, &new_policy); + + if (new_policy.governor) + module_put(new_policy.governor->owner); + return ret ? ret : count; }