linux-kernel - Re: [PATCH 3/3] driver core: class: Delete a redundant check in APIs class_(for_each|find)

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Message-ID: <2024111230-diabetic-stubbed-102b@gregkh>
Date: Tue, 12 Nov 2024 12:45:29 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org,
	Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH 3/3] driver core: class: Delete a redundant check in APIs
 class_(for_each|find)_device()

On Tue, Nov 05, 2024 at 08:20:24AM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> Delete redundant check (!@...ss) in both API class_for_each_device() and
> class_find_device() with below reasons:
> 
> - The check is covered by later check (!@sp).
> - Callers are unlikely to call both APIs with NULL class argument.
> - Make parameter check consistent with all of other class APIs.
> 
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
>  drivers/base/class.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/base/class.c b/drivers/base/class.c
> index e81da280af74..120d3aeb52fe 100644
> --- a/drivers/base/class.c
> +++ b/drivers/base/class.c
> @@ -408,8 +408,6 @@ int class_for_each_device(const struct class *class, const struct device *start,
>  	struct device *dev;
>  	int error = 0;
>  
> -	if (!class)
> -		return -EINVAL;
>  	if (!sp) {
>  		WARN(1, "%s called for class '%s' before it was registered",
>  		     __func__, class->name);

Now, if I pass in NULL for class, I get an odd warning, AND the kernel
crashes with the dereference of class->name.

So this is not ok :(

> @@ -456,8 +454,6 @@ struct device *class_find_device(const struct class *class, const struct device
>  	struct class_dev_iter iter;
>  	struct device *dev;
>  
> -	if (!class)
> -		return NULL;
>  	if (!sp) {
>  		WARN(1, "%s called for class '%s' before it was registered",
>  		     __func__, class->name);

Same here, this change is going to break things if people get it wrong,
please leave both of these as-is.

thanks,

greg k-h