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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-id: <52770837.5000901@samsung.com>
Date:	Mon, 04 Nov 2013 11:36:39 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	"Wang, Xiaoming" <xiaoming.wang@...el.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

On 11/04/2013 11:07 AM, Wang, Xiaoming wrote:
> 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?
> 

As you comment, my opinion has memory leak problem. My mistake.
But, I prefer to call 'device_unregister' at the end of extcon_dev_unregister().
To resolve kernel panic, I think we could use 'devm_kzalloc' instead of kzalloc/kfree.
What is your opinion about my approach?

Thanks,
Chanwoo Choi


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/