Message-ID: <1449432742.2515.20.camel@tiscali.nl>
Subject: Re: gigaset: freeing an active object
From: Paul Bolle <pebolle@tiscali.nl>
To: Tilman Schmidt <tilman@imap.cc>, Peter Hurley <peter@hurleysoftware.com>,
        Sasha Levin <sasha.levin@oracle.com>
Cc: isdn@linux-pingi.de, davem@davemloft.net,
        gigaset307x-common@lists.sourceforge.net,
        LKML <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        syzkaller <syzkaller@googlegroups.com>
Date: Sun, 06 Dec 2015 21:12:22 +0100
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On zo, 2015-12-06 at 16:29 +0100, Tilman Schmidt wrote:
> So the solution might be as simple as moving the kfree() call from
> gigaset_freecshw() to gigaset_device_release(). Something like this:
> 
> --- a/drivers/isdn/gigaset/ser-gigaset.c
> +++ b/drivers/isdn/gigaset/ser-gigaset.c
> @@ -370,19 +370,18 @@ 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;
>  }

This solution assumes that the struct platform_device is moved out of
the struct ser_cardstate, doesn't it? In other words, this is something
to do on top of my (draft) patch. Otherwise we'd still be freeing memory
managed through reference counting.

Thanks,


Paul Bolle
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