Subject: [PATCH] extcon: Fix missing locking when [un]registering notifiers

From: [email-masked] (Chanwoo Choi)
Date: Mon, 23 Mar 2015 12:00:24 +0900

Hi Hans,

Looks good to me of this patch.

But,
I have some comment. You have to send extcon patch to linux-kernel at vger.kerne.org mailing list
but you missed it. Also if you fixes extcon driver, you should develop them on extcon git repository
because extcon-class.c was renamed to extcon.c. I added the extcon git repository and branch name.
- git repo : http://git.kernel.org/cgit/linux/kernel/git/chanwoo/extcon.git/
- branch : extcon-next

After I modified this patch without apply conflict personally,
I applied it on extcon-next branch.

Thanks,
Chanwoo Choi

On 03/22/2015 01:26 AM, Hans de Goede wrote:
> Since extcon-class.c is using raw_notifiers it must protect the notifier
> list itself when [un]registering notifiers to avoid the list changing while
> extcon_update_state is walking the list (through raw_notifier_call_chain).
> 
> Signed-off-by: Hans de Goede <[email-masked]>
> ---
>  drivers/extcon/extcon-class.c | 35 +++++++++++++++++++++++++++++++----
>  1 file changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/extcon/extcon-class.c b/drivers/extcon/extcon-class.c
> index 8319f25..b079c41 100644
> --- a/drivers/extcon/extcon-class.c
> +++ b/drivers/extcon/extcon-class.c
> @@ -444,6 +444,9 @@ int extcon_register_interest(struct extcon_specific_cable_nb *obj,
>  			     const char *extcon_name, const char *cable_name,
>  			     struct notifier_block *nb)
>  {
> +	unsigned long flags;
> +	int ret;
> +
>  	if (!obj || !cable_name || !nb)
>  		return -EINVAL;
>  
> @@ -461,8 +464,11 @@ int extcon_register_interest(struct extcon_specific_cable_nb *obj,
>  
>  		obj->internal_nb.notifier_call = _call_per_cable;
>  
> -		return raw_notifier_chain_register(&obj->edev->nh,
> +		spin_lock_irqsave(&obj->edev->lock, flags);
> +		ret = raw_notifier_chain_register(&obj->edev->nh,
>  						  &obj->internal_nb);
> +		spin_unlock_irqrestore(&obj->edev->lock, flags);
> +		return ret;
>  	} else {
>  		struct class_dev_iter iter;
>  		struct extcon_dev *extd;
> @@ -495,10 +501,17 @@ EXPORT_SYMBOL_GPL(extcon_register_interest);
>   */
>  int extcon_unregister_interest(struct extcon_specific_cable_nb *obj)
>  {
> +	unsigned long flags;
> +	int ret;
> +
>  	if (!obj)
>  		return -EINVAL;
>  
> -	return raw_notifier_chain_unregister(&obj->edev->nh, &obj->internal_nb);
> +	spin_lock_irqsave(&obj->edev->lock, flags);
> +	ret = raw_notifier_chain_unregister(&obj->edev->nh, &obj->internal_nb);
> +	spin_unlock_irqrestore(&obj->edev->lock, flags);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(extcon_unregister_interest);
>  
> @@ -515,7 +528,14 @@ EXPORT_SYMBOL_GPL(extcon_unregister_interest);
>  int extcon_register_notifier(struct extcon_dev *edev,
>  			struct notifier_block *nb)
>  {
> -	return raw_notifier_chain_register(&edev->nh, nb);
> +	unsigned long flags;
> +	int ret;
> +
> +	spin_lock_irqsave(&edev->lock, flags);
> +	ret = raw_notifier_chain_register(&edev->nh, nb);
> +	spin_unlock_irqrestore(&edev->lock, flags);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(extcon_register_notifier);
>  
> @@ -527,7 +547,14 @@ EXPORT_SYMBOL_GPL(extcon_register_notifier);
>  int extcon_unregister_notifier(struct extcon_dev *edev,
>  			struct notifier_block *nb)
>  {
> -	return raw_notifier_chain_unregister(&edev->nh, nb);
> +	unsigned long flags;
> +	int ret;
> +
> +	spin_lock_irqsave(&edev->lock, flags);
> +	ret = raw_notifier_chain_unregister(&edev->nh, nb);
> +	spin_unlock_irqrestore(&edev->lock, flags);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(extcon_unregister_notifier);
>  
>