| Message ID | 1353492634-10730-1-git-send-email-myungjoo.ham@samsung.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
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 <keescook@chromium.org> > Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Quoting Serge E. Hallyn (serge@hallyn.com): > 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(). > > Well, to be honest, the opp locking isn't 100% clear to me, but IIUC (1) things can be added but never removed, (2) opp_get_notifier doesn't pin a refcount on what it returns, but it returns something which won't be deleted. So IIUC what's below is fine, bc it doesn't need to pin the nh for the nh to remain valid outside of the rcu_read_lock. If I'm wrong about that, then the below is not sufficient. > Reviewed-by: Serge Hallyn <serge.hallyn@canonical.com> > > > Reported-by: Kees Cook <keescook@chromium.org> > > Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> > > --- > > 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 1388d46..5275883 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); > > + rcu_read_unlock(); > > + if (!ret) > > + ret = srcu_notifier_chain_register(nh, &devfreq->nb); > > + > > + return ret; > > } > > > > /** > > @@ -1042,11 +1049,18 @@ int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq) > > */ > > int devfreq_unregister_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_unregister(nh, &devfreq->nb); > > + ret = PTR_ERR(nh); > > + rcu_read_unlock(); > > + if (!ret) > > + ret = srcu_notifier_chain_unregister(nh, &devfreq->nb); > > + > > + return ret; > > } > > > > MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>"); > > -- > > 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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); + rcu_read_unlock(); + + return ret; } /** @@ -1042,11 +1049,18 @@ int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq) */ int devfreq_unregister_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_unregister(nh, &devfreq->nb); + ret = PTR_ERR(nh); + if (!ret) + ret = srcu_notifier_chain_unregister(nh, &devfreq->nb); + rcu_read_unlock(); + + return ret; } MODULE_AUTHOR("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 <keescook@chromium.org> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> --- drivers/devfreq/devfreq.c | 26 ++++++++++++++++++++------ 1 files changed, 20 insertions(+), 6 deletions(-)