Re: [PATCH 7/9] thermal/core: Protect sysfs accesses to thermal operations with thermal zone mutex

[Rafael J. Wysocki]

On Mon, Oct 17, 2022 at 3:09 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> Protect access to thermal operations against thermal zone removal by
> acquiring the thermal zone device mutex. After acquiring the mutex, check
> if the thermal zone device is registered and abort the operation if not.
>
> With this change, we can call __thermal_zone_device_update() instead of
> thermal_zone_device_update() from trip_point_temp_store() and from
> emul_temp_store(). Similar, we can call __thermal_zone_set_trips() instead
> of thermal_zone_set_trips() from trip_point_hyst_store().
>
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
>  drivers/thermal/thermal_core.c  |  4 +-
>  drivers/thermal/thermal_core.h  |  2 +
>  drivers/thermal/thermal_sysfs.c | 77 ++++++++++++++++++++++++++++-----
>  3 files changed, 69 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 9facd9c5b70f..b8e3b262b2bd 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -403,8 +403,8 @@ static void thermal_zone_device_init(struct thermal_zone_device *tz)
>                 pos->initialized = false;
>  }
>
> -static void __thermal_zone_device_update(struct thermal_zone_device *tz,
> -                                        enum thermal_notify_event event)
> +void __thermal_zone_device_update(struct thermal_zone_device *tz,
> +                                 enum thermal_notify_event event)
>  {
>         int count;
>
> diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
> index 1571917bd3c8..7b51b9a22e7e 100644
> --- a/drivers/thermal/thermal_core.h
> +++ b/drivers/thermal/thermal_core.h
> @@ -109,6 +109,8 @@ int thermal_register_governor(struct thermal_governor *);
>  void thermal_unregister_governor(struct thermal_governor *);
>  int thermal_zone_device_set_policy(struct thermal_zone_device *, char *);
>  int thermal_build_list_of_policies(char *buf);
> +void __thermal_zone_device_update(struct thermal_zone_device *tz,
> +                                 enum thermal_notify_event event);
>
>  /* Helpers */
>  void thermal_zone_set_trips(struct thermal_zone_device *tz);
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index ec495c7dff03..68607e6070e8 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -92,7 +92,15 @@ trip_point_type_show(struct device *dev, struct device_attribute *attr,
>         if (sscanf(attr->attr.name, "trip_point_%d_type", &trip) != 1)
>                 return -EINVAL;
>
> +       mutex_lock(&tz->lock);
> +
> +       if (!device_is_registered(dev)) {
> +               mutex_unlock(&tz->lock);
> +               return -ENODEV;
> +       }
> +
>         result = tz->ops->get_trip_type(tz, trip, &type);
> +       mutex_unlock(&tz->lock);
>         if (result)
>                 return result;
>
> @@ -128,10 +136,17 @@ trip_point_temp_store(struct device *dev, struct device_attribute *attr,
>         if (kstrtoint(buf, 10, &temperature))
>                 return -EINVAL;
>
> +       mutex_lock(&tz->lock);
> +
> +       if (!device_is_registered(dev)) {
> +               ret = -ENODEV;
> +               goto unlock;
> +       }
> +
>         if (tz->ops->set_trip_temp) {
>                 ret = tz->ops->set_trip_temp(tz, trip, temperature);
>                 if (ret)
> -                       return ret;
> +                       goto unlock;
>         }
>
>         if (tz->trips)
> @@ -140,18 +155,21 @@ trip_point_temp_store(struct device *dev, struct device_attribute *attr,
>         if (tz->ops->get_trip_hyst) {
>                 ret = tz->ops->get_trip_hyst(tz, trip, &hyst);
>                 if (ret)
> -                       return ret;
> +                       goto unlock;
>         }
>
>         ret = tz->ops->get_trip_type(tz, trip, &type);
>         if (ret)
> -               return ret;
> +               goto unlock;
>
>         thermal_notify_tz_trip_change(tz->id, trip, type, temperature, hyst);
>
> -       thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> +       __thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
>
> -       return count;
> +unlock:
> +       mutex_unlock(&tz->lock);
> +
> +       return ret ? ret : count;
>  }
>
>  static ssize_t
> @@ -168,12 +186,19 @@ trip_point_temp_show(struct device *dev, struct device_attribute *attr,
>         if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip) != 1)
>                 return -EINVAL;
>
> +       mutex_lock(&tz->lock);
> +
> +       if (!device_is_registered(dev)) {
> +               ret = -ENODEV;
> +               goto unlock;
> +       }
> +
>         ret = tz->ops->get_trip_temp(tz, trip, &temperature);
>

Well, this is a pattern I've already talked about twice, so let me
just mention it here.

> -       if (ret)
> -               return ret;
> +unlock:
> +       mutex_unlock(&tz->lock);
>
> -       return sprintf(buf, "%d\n", temperature);
> +       return ret ? ret : sprintf(buf, "%d\n", temperature);

And I wouldn't change this (like in the other patch I've commented).

>  }
>
>  static ssize_t
> @@ -193,6 +218,13 @@ trip_point_hyst_store(struct device *dev, struct device_attribute *attr,
>         if (kstrtoint(buf, 10, &temperature))
>                 return -EINVAL;
>
> +       mutex_lock(&tz->lock);
> +
> +       if (!device_is_registered(dev)) {
> +               ret = -ENODEV;
> +               goto unlock;
> +       }
> +
>         /*
>          * We are not doing any check on the 'temperature' value
>          * here. The driver implementing 'set_trip_hyst' has to
> @@ -201,7 +233,10 @@ trip_point_hyst_store(struct device *dev, struct device_attribute *attr,
>         ret = tz->ops->set_trip_hyst(tz, trip, temperature);
>
>         if (!ret)
> -               thermal_zone_set_trips(tz);
> +               __thermal_zone_set_trips(tz);
> +
> +unlock:
> +       mutex_unlock(&tz->lock);
>
>         return ret ? ret : count;
>  }
> @@ -220,8 +255,18 @@ trip_point_hyst_show(struct device *dev, struct device_attribute *attr,
>         if (sscanf(attr->attr.name, "trip_point_%d_hyst", &trip) != 1)
>                 return -EINVAL;
>
> +       mutex_lock(&tz->lock);
> +
> +       if (!device_is_registered(dev)) {
> +               ret = -ENODEV;
> +               goto unlock;
> +       }
> +
>         ret = tz->ops->get_trip_hyst(tz, trip, &temperature);

Same pattern again.

> +unlock:
> +       mutex_unlock(&tz->lock);
> +
>         return ret ? ret : sprintf(buf, "%d\n", temperature);
>  }
>
> @@ -269,16 +314,24 @@ emul_temp_store(struct device *dev, struct device_attribute *attr,
>         if (kstrtoint(buf, 10, &temperature))
>                 return -EINVAL;
>
> +       mutex_lock(&tz->lock);
> +
> +       if (!device_is_registered(dev)) {
> +               ret = -ENODEV;
> +               goto unlock;
> +       }
> +
>         if (!tz->ops->set_emul_temp) {
> -               mutex_lock(&tz->lock);
>                 tz->emul_temperature = temperature;
> -               mutex_unlock(&tz->lock);
>         } else {
>                 ret = tz->ops->set_emul_temp(tz, temperature);
>         }

Drop the leftover braces that are not necessary now?

>
>         if (!ret)
> -               thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> +               __thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> +
> +unlock:
> +       mutex_unlock(&tz->lock);
>
>         return ret ? ret : count;
>  }
> --