linux-kernel - Re: [PATCH v1] thermal: core: Fix use-after-free in thermal_zone_device

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Date:   Tue, 18 Aug 2020 02:54:50 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] thermal: core: Fix use-after-free in
 thermal_zone_device_unregister()

18.08.2020 02:48, Dmitry Osipenko пишет:
> The user-after-free bug in thermal_zone_device_unregister() is reported by
> KASAN. It happens because struct thermal_zone_device is released during of
> device_unregister() invocation, and hence the "tz" variable shouldn't be
> touched by thermal_notify_tz_delete(tz->id).
> 
> Fixes: 55cdf0a283b8 ("thermal: core: Add notifications call in the framework")
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/thermal/thermal_core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 72bf159bcecc..56c355f684df 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -1516,7 +1516,7 @@ EXPORT_SYMBOL_GPL(thermal_zone_device_register);
>   */
>  void thermal_zone_device_unregister(struct thermal_zone_device *tz)
>  {
> -	int i;
> +	int i, tz_id;
>  	const struct thermal_zone_params *tzp;
>  	struct thermal_cooling_device *cdev;
>  	struct thermal_zone_device *pos = NULL;
> @@ -1525,6 +1525,7 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
>  		return;
>  
>  	tzp = tz->tzp;
> +	tz_id = tz->id;
>  
>  	mutex_lock(&thermal_list_lock);
>  	list_for_each_entry(pos, &thermal_tz_list, node)
> @@ -1560,14 +1561,13 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
>  	cancel_delayed_work_sync(&tz->poll_queue);
>  
>  	thermal_set_governor(tz, NULL);
> -

Woops, this line wasn't intended to be removed. Let me send a v2.

>  	thermal_remove_hwmon_sysfs(tz);
>  	ida_simple_remove(&thermal_tz_ida, tz->id);
>  	ida_destroy(&tz->ida);
>  	mutex_destroy(&tz->lock);
>  	device_unregister(&tz->device);
>  
> -	thermal_notify_tz_delete(tz->id);
> +	thermal_notify_tz_delete(tz_id);
>  }
>  EXPORT_SYMBOL_GPL(thermal_zone_device_unregister);
>  
>