linux-kernel - Re: [PATCH] driver core: Fix error handling in driver API device

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Message-ID: <2024071756-uproot-relieve-6e27@gregkh>
Date: Wed, 17 Jul 2024 17:03:37 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Benjamin Thery <benjamin.thery@...l.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg Kroah-Hartman <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH] driver core: Fix error handling in driver API
 device_rename()

On Wed, Jul 17, 2024 at 10:50:05PM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> Call failure of device_rename(@dev, @new_name) maybe unexpectedly change
> link name within @dev's class directory to @new_name, fixed by correcting
> error handling for the API.

I'm sorry, but I don't understand the text here, what exactly are you
doing?

> Fixes: f349cf34731c ("driver core: Implement ns directory support for device classes.")
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
>  drivers/base/core.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 2b4c0624b704..a05b7186cf33 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4512,9 +4512,11 @@ EXPORT_SYMBOL_GPL(device_destroy);
>   */
>  int device_rename(struct device *dev, const char *new_name)
>  {
> +	struct subsys_private *sp = NULL;
>  	struct kobject *kobj = &dev->kobj;
>  	char *old_device_name = NULL;
>  	int error;
> +	bool is_link_renamed = false;
>  
>  	dev = get_device(dev);
>  	if (!dev)
> @@ -4529,7 +4531,7 @@ int device_rename(struct device *dev, const char *new_name)
>  	}
>  
>  	if (dev->class) {
> -		struct subsys_private *sp = class_to_subsys(dev->class);
> +		sp = class_to_subsys(dev->class);
>  
>  		if (!sp) {
>  			error = -EINVAL;
> @@ -4537,17 +4539,20 @@ int device_rename(struct device *dev, const char *new_name)
>  		}
>  
>  		error = sysfs_rename_link_ns(&sp->subsys.kobj, kobj, old_device_name,
> -					     new_name, kobject_namespace(kobj));
> -		subsys_put(sp);
> +				new_name, kobject_namespace(kobj));

Why did you change the indentation here?

>  		if (error)
>  			goto out;
> +
> +		is_link_renamed = true;
>  	}
>  
>  	error = kobject_rename(kobj, new_name);
> -	if (error)
> -		goto out;
> -
>  out:
> +	if (error && is_link_renamed)
> +		sysfs_rename_link_ns(&sp->subsys.kobj, kobj, new_name,
> +				old_device_name, kobject_namespace(kobj));
> +	subsys_put(sp);

How was this found?  What in-kernel code causes this problem?  And how
was this tested?

thanks,

greg k-h