From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtPttEUnauQK1omamhd2BkH14pOsT2CWrvzaOZeKeDXZ6emK0IrgJn/OfIW7Dfw671o94q5 ARC-Seal: i=1; a=rsa-sha256; t=1521483352; cv=none; d=google.com; s=arc-20160816; b=xtz9gixOf93JD/po/tlskyHef54Vu9UZojQXg7TmgHwz2cnhcv5xRE98/gcfn8tizi oE5+4qrXmUca14VOwnmE+ZfAyRKFiBEPcUtgYQ5IBz8DEEBoNBDQG47XkMir12EpNJ32 TrPBYtwhw0HbSmezI6wG6JiRdjK3r9fVBuUs+iLcpE++P4k2yMrj7HYRg0DDJ4qqIwQE KSzbHE0gfabUeiunVF1EVWunb/34wHNdSFFW62yx1rH/RgqWJZ7jvhz1NR3qj+4odzsw 2hoTZrVI1EJZ1Ba2tL/5AsVSANcOaI2/asVXJpK/8iB7ZcnO4YnJ57Vnz1MVpAkGLByf exHA== 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=Y/xC9kEXQHVHh5DpR4pUf69y6tTR958p2Xgsfq1JU1o=; b=Svq0gN/g3RLxrI3nbFTfLytnbyjLa61UTJNsc/9yssGU/ChDLQeoevNYdvetlLl5CL x7AfVXDeBqXtvkS9o9wA6oiYikgA4Jod9vw9/033veFthMQp16S70V4KH1VYdUanOjL8 EnACYF5JSTebba5tOTBqrrmzqTJXIHEIDP8KxJnqdolmFwuHH7Kxb4k05QKVWPV88QlR 556DDexq7yqYTYN/n/h5nWvS640b8+B0JKNi96/CeY4bB/GBTXwvEP5i2ZMFMGMrGzeV 1AIEIjCEnsWw1GUhS3c+y+3DYVFiciL+YlEYrs6HatH/LtsdHY6n+S6MQfgEYtzxF7Xv 6L9g== 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 4.4 092/134] cpufreq: Fix governor module removal race Date: Mon, 19 Mar 2018 19:06:15 +0100 Message-Id: <20180319171902.578082436@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180319171849.024066323@linuxfoundation.org> References: <20180319171849.024066323@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?1595390927744329142?= X-GMAIL-MSGID: =?utf-8?q?1595390927744329142?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.4-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 @@ -551,6 +551,8 @@ static int cpufreq_parse_governor(char * *governor = t; err = 0; } + if (t && !try_module_get(t->owner)) + t = NULL; mutex_unlock(&cpufreq_governor_mutex); } @@ -669,6 +671,10 @@ 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; }