linux-kernel - RE: [PATCH] [extcon]:remove freed groups caused the panic or warning in unregister flow

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Message-ID: <FA47D36D6EC9FE4CB463299737C09B9901B6467C@SHSMSX102.ccr.corp.intel.com>
Date:	Mon, 4 Nov 2013 02:07:32 +0000
From:	"Wang, Xiaoming" <xiaoming.wang@...el.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
CC:	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Liu, Chuansheng" <chuansheng.liu@...el.com>,
	"Zhang, Dongxing" <dongxing.zhang@...el.com>
Subject: RE: [PATCH] [extcon]:remove freed groups caused the panic or
 warning in unregister flow

Dear Choi

-----Original Message-----
From: Chanwoo Choi [mailto:cw00.choi@...sung.com] 
Sent: Monday, November 04, 2013 9:43 AM
To: Wang, Xiaoming
Cc: myungjoo.ham@...sung.com; linux-kernel@...r.kernel.org; Liu, Chuansheng; Zhang, Dongxing
Subject: Re: [PATCH] [extcon]:remove freed groups caused the panic or warning in unregister flow

Hi Wang,

>  drivers/extcon/extcon-class.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/extcon/extcon-class.c 
> b/drivers/extcon/extcon-class.c index 148382f..48f4669 100644
> --- a/drivers/extcon/extcon-class.c
> +++ b/drivers/extcon/extcon-class.c
> @@ -794,6 +794,8 @@ void extcon_dev_unregister(struct extcon_dev *edev)
>  		return;
>  	}
>  
> +	device_unregister(edev->dev);
> +
>  	if (edev->mutually_exclusive && edev->max_supported) {
>  		for (index = 0; edev->mutually_exclusive[index];
>  				index++)
> @@ -814,7 +816,6 @@ void extcon_dev_unregister(struct extcon_dev *edev)
>  	if (switch_class)
>  		class_compat_remove_link(switch_class, edev->dev, NULL);  #endif
> -	device_unregister(edev->dev);
>  	put_device(edev->dev);
>  }
>  EXPORT_SYMBOL_GPL(extcon_dev_unregister);
> 

I think we could only apply following patch instead of moving the position of device_unregister().

diff --git a/drivers/extcon/extcon-class.c b/drivers/extcon/extcon-class.c index 148382f..ff27b19 100644
--- a/drivers/extcon/extcon-class.c
+++ b/drivers/extcon/extcon-class.c
@@ -805,10 +805,8 @@ void extcon_dev_unregister(struct extcon_dev *edev)
        for (index = 0; index < edev->max_supported; index++)
                kfree(edev->cables[index].attr_g.name);
 
-       if (edev->max_supported) {
-               kfree(edev->extcon_dev_type.groups);
+       if (edev->max_supported)
                kfree(edev->cables);
-       }
 
 #if defined(CONFIG_ANDROID)
        if (switch_class)

Thanks,
Chanwoo Choi

	I don't agree with you.
	Why do not you want moving the position of device_unregister()?
	It will cause the memory leak if has not kfree edev->extcon_dev_type.groups as your patch do firstly. And if you think kfree edev->extcon_dev_type.groups is meaningless well then kfree edev->extcon_dev_type.groups in function exton_dev_register (line 756)also should be removed I think. What do you think?

Thanks
Xiaoming.