From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753968Ab2KUNmR (ORCPT ); Wed, 21 Nov 2012 08:42:17 -0500 Received: from 50-56-35-84.static.cloud-ips.com ([50.56.35.84]:38268 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751640Ab2KUNmP (ORCPT ); Wed, 21 Nov 2012 08:42:15 -0500 Date: Wed, 21 Nov 2012 13:46:21 +0000 From: "Serge E. Hallyn" To: MyungJoo Ham Cc: linux-pm@vger.kernel.org, rjw@sisk.pl, keescook@chromium.org, serge.hallyn@canonical.com, linux-kernel@vger.kernel.org, myungjoo.ham@gmail.com Subject: Re: [PATCH] PM / devfreq: missing rcu_read_lock() added for find_device_opp() Message-ID: <20121121134621.GA30575@mail.hallyn.com> References: <1353492634-10730-1-git-send-email-myungjoo.ham@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1353492634-10730-1-git-send-email-myungjoo.ham@samsung.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting MyungJoo Ham (myungjoo.ham@samsung.com): > opp_get_notifier() uses find_device_opp(), which requires to > held rcu_read_lock. In order to keep the notifier-header > valid, we have added rcu_read_lock(). > > Reported-by: Kees Cook > Signed-off-by: MyungJoo Ham > --- > drivers/devfreq/devfreq.c | 26 ++++++++++++++++++++------ > 1 files changed, 20 insertions(+), 6 deletions(-) > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > index 45e053e..e91cb22 100644 > --- a/drivers/devfreq/devfreq.c > +++ b/drivers/devfreq/devfreq.c > @@ -1023,11 +1023,18 @@ struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq, > */ > int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq) > { > - struct srcu_notifier_head *nh = opp_get_notifier(dev); > + struct srcu_notifier_head *nh; > + int ret = 0; > > + rcu_read_lock(); > + nh = opp_get_notifier(dev); > if (IS_ERR(nh)) > - return PTR_ERR(nh); > - return srcu_notifier_chain_register(nh, &devfreq->nb); > + ret = PTR_ERR(nh); > + if (!ret) > + ret = srcu_notifier_chain_register(nh, &devfreq->nb); Hm, but if I'm seeing right, srcu_notifier_chain_register calls mutex_lock(), which sleeps, so you can't do that under rcu_read_lock(). -serge