Re: [PATCH v1] thermal: core: Fix NULL pointer dereference in zone registration error path

[Lukasz Luba <lukasz.luba@arm.com>]

On 12/14/23 10:52, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> If device_register() in thermal_zone_device_register_with_trips()
> returns an error, the tz variable is set to NULL and subsequently
> dereferenced in kfree(tz->tzp).
> 
> Commit adc8749b150c ("thermal/drivers/core: Use put_device() if
> device_register() fails") added the tz = NULL assignment in question to
> avoid a possible double-free after dropping the reference to the zone
> device.  However, after commit 4649620d9404 ("thermal: core: Make
> thermal_zone_device_unregister() return after freeing the zone"), that
> assignment has become redundant, because dropping the reference to the
> zone device does not cause the zone object to be freed any more.
> 
> Drop it to address the NULL pointer dereference.
> 
> Fixes: 3d439b1a2ad3 ("thermal/core: Alloc-copy-free the thermal zone parameters structure")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>   drivers/thermal/thermal_core.c |    1 -
>   1 file changed, 1 deletion(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -1394,7 +1394,6 @@ unregister:
>   	device_del(&tz->device);
>   release_device:
>   	put_device(&tz->device);
> -	tz = NULL;
>   remove_id:
>   	ida_free(&thermal_tz_ida, id);
>   free_tzp:
> 
> 
> 

Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>