linux-kernel - Re: [PATCH 3/6] parport: Remove register_sysctl_table from parport_device_proc

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Date:   Mon, 15 May 2023 21:10:19 +0200
From:   Joel Granados <j.granados@...sung.com>
To:     <mcgrof@...nel.org>
CC:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 3/6] parport: Remove register_sysctl_table from
 parport_device_proc_register

On Mon, May 15, 2023 at 09:14:43AM +0200, Joel Granados wrote:
> This is part of the general push to deprecate register_sysctl_paths and
> register_sysctl_table. We use a temp allocation to include both port and
> device name in proc. Allocated mem is freed at the end. The unused
> parport_device_sysctl_template struct elements that are not used are
> removed.
> 
> Signed-off-by: Joel Granados <j.granados@...sung.com>
> ---
>  drivers/parport/procfs.c | 57 +++++++++++++++++++++++-----------------
>  1 file changed, 33 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
> index 53ae5cb98190..902547eb045c 100644
> --- a/drivers/parport/procfs.c
> +++ b/drivers/parport/procfs.c
> @@ -384,6 +384,7 @@ parport_device_sysctl_template = {
>  			.extra1		= (void*) &parport_min_timeslice_value,
>  			.extra2		= (void*) &parport_max_timeslice_value
>  		},
> +		{}
>  	},
>  	{
>  		{
> @@ -394,22 +395,6 @@ parport_device_sysctl_template = {
>  			.child		= NULL
>  		},
>  		{}
> -	},
> -	{
> -		PARPORT_DEVICES_ROOT_DIR,
> -		{}
> -	},
> -	{
> -		PARPORT_PORT_DIR(NULL),
> -		{}
> -	},
> -	{
> -		PARPORT_PARPORT_DIR(NULL),
> -		{}
> -	},
> -	{
> -		PARPORT_DEV_DIR(NULL),
> -		{}
>  	}
>  };
>  
> @@ -547,30 +532,54 @@ int parport_proc_unregister(struct parport *port)
>  
>  int parport_device_proc_register(struct pardevice *device)
>  {
> +	int err = 0;
>  	struct parport_device_sysctl_table *t;
>  	struct parport * port = device->port;
> +	size_t port_name_len, device_name_len, tmp_dir_path_len;
> +	char *tmp_dir_path;
>  	
>  	t = kmemdup(&parport_device_sysctl_template, sizeof(*t), GFP_KERNEL);
>  	if (t == NULL)
>  		return -ENOMEM;
>  
> -	t->dev_dir[0].child = t->parport_dir;
> -	t->parport_dir[0].child = t->port_dir;
> -	t->port_dir[0].procname = port->name;
> -	t->port_dir[0].child = t->devices_root_dir;
> -	t->devices_root_dir[0].child = t->device_dir;
> +	port_name_len = strnlen(port->name, PARPORT_NAME_MAX_LEN);
> +	device_name_len = strnlen(device->name, PATH_MAX);
> +
> +	/* Allocate a buffer for two paths: dev/parport/PORT/devices/DEVICE. */
> +	tmp_dir_path_len = PARPORT_BASE_DEVICES_PATH_SIZE + port_name_len + device_name_len;
> +	tmp_dir_path = kmalloc(tmp_dir_path_len, GFP_KERNEL);
> +	if (!tmp_dir_path) {
> +		err = -ENOMEM;
> +		goto exit_free_t;
> +	}
> +
> +	if (tmp_dir_path_len
> +	    <= snprintf(tmp_dir_path, tmp_dir_path_len, "dev/parport/%s/devices/%s",
> +			port->name, device->name)) {
> +		err = -ENOENT;
> +		goto exit_free_path;
> +	}
>  
> -	t->device_dir[0].procname = device->name;
> -	t->device_dir[0].child = t->vars;
>  	t->vars[0].data = &device->timeslice;
>  
> -	t->sysctl_header = register_sysctl_table(t->dev_dir);
> +	t->sysctl_header = register_sysctl(tmp_dir_path, t->vars);
>  	if (t->sysctl_header == NULL) {
>  		kfree(t);
>  		t = NULL;
In the paprport_proc_register there is the same logic where we do not
return error code on error. Additionally, noone checks the return values
of parport_proc_register nor parport_device_proc_register. Should we
just change these to void and be done with it? Or is it better to change
parport/share.c to take care of the error codes?

I realized this after some comments from 0-day.

Best


>  	}
>  	device->sysctl_table = t;
> +
> +	kfree(tmp_dir_path);
>  	return 0;
> +
> +exit_free_path:
> +	kfree(tmp_dir_path);
> +
> +exit_free_t:
> +	kfree(t);
> +	t = NULL;
> +
> +	return err;
>  }
>  
>  int parport_device_proc_unregister(struct pardevice *device)
> -- 
> 2.30.2
> 

-- 

Joel Granados

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