linux-kernel - Re: [PATCH 3.4 088/125] ser_gigaset: fix deallocation of platform device structure

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Date:   Wed, 12 Oct 2016 14:52:20 +0200
From:   Paul Bolle <pebolle@...cali.nl>
To:     lizf@...nel.org, stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Tilman Schmidt <tilman@...p.cc>,
        "David S. Miller" <davem@...emloft.net>,
        Zefan Li <lizefan@...wei.com>
Subject: Re: [PATCH 3.4 088/125] ser_gigaset: fix deallocation of platform
 device structure

Zefan Li,

On Wed, 2016-10-12 at 20:33 +0800, lizf@...nel.org wrote:
> When shutting down the device, the struct ser_cardstate must not be
> kfree()d immediately after the call to platform_device_unregister()
> since the embedded struct platform_device is still in use.
> Move the kfree() call to the release method instead.
> 
> Signed-off-by: Tilman Schmidt <tilman@...p.cc>
> Fixes: 2869b23e4b95 ("drivers/isdn/gigaset: new M101 driver (v2)")
> Reported-by: Sasha Levin <sasha.levin@...cle.com>
> Signed-off-by: Paul Bolle <pebolle@...cali.nl>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Zefan Li <lizefan@...wei.com>

There has been a follow up for this fix. I'll have to dive into my
archive to see why that was needed.

It was complicated, because there has been a short period in which this
fix was correct. Something like that, I'm speaking from memory.
(Perhaps Tilman's memory is less imperfect.)

I'll try get back to this shortly (in a day or so).

Thanks,


Paul Bolle

> ---
>  drivers/isdn/gigaset/ser-gigaset.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/isdn/gigaset/ser-gigaset.c
> b/drivers/isdn/gigaset/ser-gigaset.c
> index 6f3fd4c..3cdfcd0 100644
> --- a/drivers/isdn/gigaset/ser-gigaset.c
> +++ b/drivers/isdn/gigaset/ser-gigaset.c
> @@ -371,19 +371,23 @@ static void gigaset_freecshw(struct cardstate
> *cs)
>  	tasklet_kill(&cs->write_tasklet);
>  	if (!cs->hw.ser)
>  		return;
> -	dev_set_drvdata(&cs->hw.ser->dev.dev, NULL);
>  	platform_device_unregister(&cs->hw.ser->dev);
> -	kfree(cs->hw.ser);
> -	cs->hw.ser = NULL;
>  }
>  
>  static void gigaset_device_release(struct device *dev)
>  {
>  	struct platform_device *pdev = to_platform_device(dev);
> +	struct cardstate *cs = dev_get_drvdata(dev);
>  
>  	/* adapted from platform_device_release() in
> drivers/base/platform.c */
>  	kfree(dev->platform_data);
>  	kfree(pdev->resource);
> +
> +	if (!cs)
> +		return;
> +	dev_set_drvdata(dev, NULL);
> +	kfree(cs->hw.ser);
> +	cs->hw.ser = NULL;
>  }
>  
>  /*