* [PATCH] PM / devfreq: stopping the governor before device_unregister() @ 2018-08-30 10:02 ` vincent.donnefort 2018-08-31 8:52 ` Chanwoo Choi 0 siblings, 1 reply; 4+ messages in thread From: vincent.donnefort @ 2018-08-30 10:02 UTC (permalink / raw) To: myungjoo.ham, kyungmin.park, cw00.choi, linux-pm, linux-kernel Cc: john.reitan, beata.michalska, Vincent Donnefort From: Vincent Donnefort <vincent.donnefort@arm.com> device_release() is freeing the resources before calling the device specific release callback which is, in the case of devfreq, stopping the governor. It is a problem as some governors are using the device resources. e.g. simpleondemand which is using the devfreq deferrable monitoring work. If it is not stopped before the resources are freed, it might lead to a use after free. Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Reviewed-by: John Einar Reitan <john.reitan@arm.com> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index 4c49bb1..4e43830 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -534,10 +534,6 @@ static void devfreq_dev_release(struct device *dev) list_del(&devfreq->node); mutex_unlock(&devfreq_list_lock); - if (devfreq->governor) - devfreq->governor->event_handler(devfreq, - DEVFREQ_GOV_STOP, NULL); - if (devfreq->profile->exit) devfreq->profile->exit(devfreq->dev.parent); @@ -672,7 +668,7 @@ struct devfreq *devfreq_add_device(struct device *dev, list_del(&devfreq->node); mutex_unlock(&devfreq_list_lock); - device_unregister(&devfreq->dev); + devfreq_remove_device(devfreq); devfreq = NULL; err_dev: if (devfreq) @@ -693,6 +689,9 @@ int devfreq_remove_device(struct devfreq *devfreq) if (!devfreq) return -EINVAL; + if (devfreq->governor) + devfreq->governor->event_handler(devfreq, + DEVFREQ_GOV_STOP, NULL); device_unregister(&devfreq->dev); return 0; -- 1.9.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] PM / devfreq: stopping the governor before device_unregister() 2018-08-30 10:02 ` [PATCH] PM / devfreq: stopping the governor before device_unregister() vincent.donnefort @ 2018-08-31 8:52 ` Chanwoo Choi 2018-09-21 15:40 ` [PATCH v2] PM / devfreq: Stop " vincent.donnefort 0 siblings, 1 reply; 4+ messages in thread From: Chanwoo Choi @ 2018-08-31 8:52 UTC (permalink / raw) To: vincent.donnefort, myungjoo.ham, kyungmin.park, linux-pm, linux-kernel Cc: john.reitan, beata.michalska Hi, On 2018년 08월 30일 19:02, vincent.donnefort@arm.com wrote: > From: Vincent Donnefort <vincent.donnefort@arm.com> > > device_release() is freeing the resources before calling the device > specific release callback which is, in the case of devfreq, stopping > the governor. > > It is a problem as some governors are using the device resources. e.g. > simpleondemand which is using the devfreq deferrable monitoring work. If it > is not stopped before the resources are freed, it might lead to a use after > free. > > Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> > Reviewed-by: John Einar Reitan <john.reitan@arm.com> > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > index 4c49bb1..4e43830 100644 > --- a/drivers/devfreq/devfreq.c > +++ b/drivers/devfreq/devfreq.c > @@ -534,10 +534,6 @@ static void devfreq_dev_release(struct device *dev) > list_del(&devfreq->node); > mutex_unlock(&devfreq_list_lock); > > - if (devfreq->governor) > - devfreq->governor->event_handler(devfreq, > - DEVFREQ_GOV_STOP, NULL); > - > if (devfreq->profile->exit) > devfreq->profile->exit(devfreq->dev.parent); > > @@ -672,7 +668,7 @@ struct devfreq *devfreq_add_device(struct device *dev, > list_del(&devfreq->node); > mutex_unlock(&devfreq_list_lock); > > - device_unregister(&devfreq->dev); > + devfreq_remove_device(devfreq); > devfreq = NULL; > err_dev: > if (devfreq) > @@ -693,6 +689,9 @@ int devfreq_remove_device(struct devfreq *devfreq) > if (!devfreq) > return -EINVAL; > > + if (devfreq->governor) > + devfreq->governor->event_handler(devfreq, > + DEVFREQ_GOV_STOP, NULL); > device_unregister(&devfreq->dev); > > return 0; > As description of this patch, if devfreq_wq is executed and then execute the 'devfreq->governor->get_target_freq' between step1 and step2 after already freed the 'dev' related resource, it might happen the problem because the registered callback of get_target_freq requires the 'dev' resource. device_unregister(dev) step 1. device_del(dev) <- if devfreq_wq is executed step 2. put_device(dev) device_release() devfreq_dev_release() stop the governor for specific devfreq instance It looks good to me. Stop the governor before calling device_unregister(). Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> -- Best Regards, Chanwoo Choi Samsung Electronics ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] PM / devfreq: Stop the governor before device_unregister() 2018-08-31 8:52 ` Chanwoo Choi @ 2018-09-21 15:40 ` vincent.donnefort 2018-09-27 5:20 ` MyungJoo Ham 0 siblings, 1 reply; 4+ messages in thread From: vincent.donnefort @ 2018-09-21 15:40 UTC (permalink / raw) To: myungjoo.ham, kyungmin.park, cw00.choi, linux-pm, linux-kernel Cc: john.reitan, beata.michalska, Vincent Donnefort From: Vincent Donnefort <vincent.donnefort@arm.com> device_release() is freeing the resources before calling the device specific release callback which is, in the case of devfreq, stopping the governor. It is a problem as some governors are using the device resources. e.g. simpleondemand which is using the devfreq deferrable monitoring work. If it is not stopped before the resources are freed, it might lead to a use after free. Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Reviewed-by: John Einar Reitan <john.reitan@arm.com> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index 4c49bb1..4e43830 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -534,10 +534,6 @@ static void devfreq_dev_release(struct device *dev) list_del(&devfreq->node); mutex_unlock(&devfreq_list_lock); - if (devfreq->governor) - devfreq->governor->event_handler(devfreq, - DEVFREQ_GOV_STOP, NULL); - if (devfreq->profile->exit) devfreq->profile->exit(devfreq->dev.parent); @@ -672,7 +668,7 @@ struct devfreq *devfreq_add_device(struct device *dev, list_del(&devfreq->node); mutex_unlock(&devfreq_list_lock); - device_unregister(&devfreq->dev); + devfreq_remove_device(devfreq); devfreq = NULL; err_dev: if (devfreq) @@ -693,6 +689,9 @@ int devfreq_remove_device(struct devfreq *devfreq) if (!devfreq) return -EINVAL; + if (devfreq->governor) + devfreq->governor->event_handler(devfreq, + DEVFREQ_GOV_STOP, NULL); device_unregister(&devfreq->dev); return 0; -- 1.9.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* RE: [PATCH v2] PM / devfreq: Stop the governor before device_unregister() 2018-09-21 15:40 ` [PATCH v2] PM / devfreq: Stop " vincent.donnefort @ 2018-09-27 5:20 ` MyungJoo Ham 0 siblings, 0 replies; 4+ messages in thread From: MyungJoo Ham @ 2018-09-27 5:20 UTC (permalink / raw) To: Kyungmin Park, Chanwoo Choi, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: john.reitan@arm.com, beata.michalska@arm.com, Vincent Donnefort > From: Vincent Donnefort <vincent.donnefort@arm.com> > > device_release() is freeing the resources before calling the device > specific release callback which is, in the case of devfreq, stopping > the governor. > > It is a problem as some governors are using the device resources. e.g. > simpleondemand which is using the devfreq deferrable monitoring work. If it > is not stopped before the resources are freed, it might lead to a use after > free. > > Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> > Reviewed-by: John Einar Reitan <john.reitan@arm.com> > Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com> Cheers, MyungJoo ^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-08-30 10:02 ` [PATCH] PM / devfreq: stopping the governor before device_unregister() vincent.donnefort
2018-08-31 8:52 ` Chanwoo Choi
2018-09-21 15:40 ` [PATCH v2] PM / devfreq: Stop " vincent.donnefort
2018-09-27 5:20 ` MyungJoo Ham
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