linux-kernel - Re: [PATCH] thermal: Fix zone lookup by ID

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Message-ID: <db6efeab-b2bc-bad5-9c75-89e3e306256c@linaro.org>
Date:   Fri, 24 Jul 2020 19:12:49 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Thierry Reding <thierry.reding@...il.com>,
        Zhang Rui <rui.zhang@...el.com>
Cc:     Amit Kucheria <amitk@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thermal: Fix zone lookup by ID

Hi Thierry,

Applied, thanks for the fix!


On 24/07/2020 19:01, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> When a thermal zone is looked up by an ID and no zone is found matching
> that ID, the thermal_zone_get_by_id() function will return a pointer to
> the thermal zone list head which isn't actually a valid thermal zone.
> 
> This can lead to a subsequent crash because a valid pointer is returned
> to the called, but dereferencing that pointer as struct thermal_zone is
> not safe.
> 
> Fixes: 329b064fbd13 ("thermal: core: Get thermal zone by id")
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/thermal/thermal_core.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 007f9618e20a..9748fbb9a3a1 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -751,16 +751,18 @@ int for_each_thermal_zone(int (*cb)(struct thermal_zone_device *, void *),
>  
>  struct thermal_zone_device *thermal_zone_get_by_id(int id)
>  {
> -	struct thermal_zone_device *tz = NULL;
> +	struct thermal_zone_device *tz, *match = NULL;
>  
>  	mutex_lock(&thermal_list_lock);
>  	list_for_each_entry(tz, &thermal_tz_list, node) {
> -		if (tz->id == id)
> +		if (tz->id == id) {
> +			match = tz;
>  			break;
> +		}
>  	}
>  	mutex_unlock(&thermal_list_lock);
>  
> -	return tz;
> +	return match;
>  }
>  
>  void thermal_zone_device_unbind_exception(struct thermal_zone_device *tz,
> 


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