Re: [PATCH] drivers: pnp: proc.c: Handle errors while attaching devices

From: Leon Romanovsky <leon@kernel.org>
To: Anupama K Patil <anupamakpatil123@gmail.com>
Cc: kernelnewbies@kernelnewbies.org, gregkh@linuxfoundation.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	bkkarthik@pesu.pes.edu, linux-kernel@vger.kernel.org,
	Jaroslav Kysela <perex@perex.cz>,
	linux-acpi@vger.kernel.org, skhan@linuxfoundation.org
Subject: Re: [PATCH] drivers: pnp: proc.c: Handle errors while attaching devices
Date: Mon, 26 Apr 2021 08:04:02 +0300	[thread overview]
Message-ID: <YIZJwkux0ghJ8k9d@unreal> (raw)
In-Reply-To: <20210424194301.jmsqpycvsm7izbk3@ubuntu>

On Sun, Apr 25, 2021 at 01:13:01AM +0530, Anupama K Patil wrote:
> isapnp_proc_init() does not look at the return value from
> isapnp_proc_attach_device(). Check for this return value in
> isapnp_proc_detach_device().
> 
> Cleanup in isapnp_proc_detach_device and
> isapnp_proc_detach_bus() for cleanup.
> 
> Changed sprintf() to the kernel-space function scnprintf() as it returns
> the actual number of bytes written.
> 
> Removed unnecessary variables de, e of type 'struct proc_dir_entry' to
> save memory.

What exactly do you fix for such an old code?

> 
> Suggested-by: Shuah Khan <skhan@linuxfoundation.org>
> Co-developed-by: B K Karthik <bkkarthik@pesu.pes.edu>
> Signed-off-by: B K Karthik <bkkarthik@pesu.pes.edu>
> Signed-off-by: Anupama K Patil <anupamakpatil123@gmail.com>
> ---
>  drivers/pnp/isapnp/proc.c | 40 +++++++++++++++++++++++++++++----------
>  1 file changed, 30 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/pnp/isapnp/proc.c b/drivers/pnp/isapnp/proc.c
> index 785a796430fa..46ebc24175b7 100644
> --- a/drivers/pnp/isapnp/proc.c
> +++ b/drivers/pnp/isapnp/proc.c
> @@ -54,34 +54,54 @@ static const struct proc_ops isapnp_proc_bus_proc_ops = {
>  	.proc_read	= isapnp_proc_bus_read,
>  };
>  
> +static int isapnp_proc_detach_device(struct pnp_dev *dev)
> +{
> +	proc_remove(dev->procent);
> +	dev->procent = NULL;
> +	return 0;
> +}
> +
> +static int isapnp_proc_detach_bus(struct pnp_card *bus)
> +{
> +	proc_remove(bus->procdir);
> +	return 0;
> +}

Please don't add one line functions that are called only once and have
return value that no one care about it.

Thanks

> +
>  static int isapnp_proc_attach_device(struct pnp_dev *dev)
>  {
>  	struct pnp_card *bus = dev->card;
> -	struct proc_dir_entry *de, *e;
>  	char name[16];
>  
> -	if (!(de = bus->procdir)) {
> -		sprintf(name, "%02x", bus->number);
> -		de = bus->procdir = proc_mkdir(name, isapnp_proc_bus_dir);
> -		if (!de)
> +	if (!bus->procdir) {
> +		scnprintf(name, 16, "%02x", bus->number);
> +		bus->procdir = proc_mkdir(name, isapnp_proc_bus_dir);
> +		if (!bus->procdir)
>  			return -ENOMEM;
>  	}
> -	sprintf(name, "%02x", dev->number);
> -	e = dev->procent = proc_create_data(name, S_IFREG | S_IRUGO, de,
> +	scnprintf(name, 16, "%02x", dev->number);
> +	dev->procent = proc_create_data(name, S_IFREG | S_IRUGO, bus->procdir,
>  					    &isapnp_proc_bus_proc_ops, dev);
> -	if (!e)
> +	if (!dev->procent) {
> +		isapnp_proc_detach_bus(bus);
>  		return -ENOMEM;
> -	proc_set_size(e, 256);
> +	}
> +	proc_set_size(dev->procent, 256);
>  	return 0;
>  }
>  
>  int __init isapnp_proc_init(void)
>  {
>  	struct pnp_dev *dev;
> +	int dev_attach;
>  
>  	isapnp_proc_bus_dir = proc_mkdir("bus/isapnp", NULL);
>  	protocol_for_each_dev(&isapnp_protocol, dev) {
> -		isapnp_proc_attach_device(dev);
> +		dev_attach = isapnp_proc_attach_device(dev);
> +		if (!dev_attach) {
> +			pr_info("procfs: pnp: Unable to attach the device, not enough memory");
> +			isapnp_proc_detach_device(dev);
> +			return -ENOMEM;
> +		}
>  	}
>  	return 0;
>  }
> -- 
> 2.25.1
> 

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