Re: [PATCH v4 iwl-next] i40e: Use correct buffer size in i40e_dbg_command_read

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Kunwu Chan <chentao@kylinos.cn>
Date: Tue, 5 Dec 2023 17:58:44 +0800

> The size of "i40e_dbg_command_buf" is 256, the size of "name"
> depends on "IFNAMSIZ", plus a null character and format size,
> the total size is more than 256.
> 
> Improve readability and maintainability by replacing a hardcoded string
> allocation and formatting by the use of the kasprintf() helper.
> 
> Fixes: 02e9c290814c ("i40e: debugfs interface")
> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
> Suggested-by: Simon Horman <horms@kernel.org>
> Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com>

Your Signed-off-by must be the last tag in the block.
Perhaps the maintainer could fix it when taking, so that you wouldn't
need to send a new version only due to that.

> ---
> v2
>    - Update the size calculation with IFNAMSIZ and sizeof(i40e_dbg_command_buf)
> v3
>    - Use kasprintf to improve readability and maintainability
> v4
>    - Fix memory leak in error path
> ---
>  .../net/ethernet/intel/i40e/i40e_debugfs.c    | 20 ++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> index 88240571721a..78a7200211b2 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> @@ -72,29 +72,31 @@ static ssize_t i40e_dbg_command_read(struct file *filp, char __user *buffer,
>  {
>  	struct i40e_pf *pf = filp->private_data;
>  	int bytes_not_copied;
> -	int buf_size = 256;
>  	char *buf;
>  	int len;
>  
>  	/* don't allow partial reads */
>  	if (*ppos != 0)
>  		return 0;
> -	if (count < buf_size)
> -		return -ENOSPC;
>  
> -	buf = kzalloc(buf_size, GFP_KERNEL);
> +	buf = kasprintf(GFP_KERNEL, "%s: %s\n",
> +			pf->vsi[pf->lan_vsi]->netdev->name,
> +			i40e_dbg_command_buf);
>  	if (!buf)
>  		return -ENOSPC;
>  
> -	len = snprintf(buf, buf_size, "%s: %s\n",
> -		       pf->vsi[pf->lan_vsi]->netdev->name,
> -		       i40e_dbg_command_buf);
> +	len = strlen(buf) + 1;
> +	if (count < len)
> +		bytes_not_copied = -ENOSPC;
> +	else if (copy_to_user(buffer, buf, len))
> +		bytes_not_copied = -EFAULT;
> +	else
> +		bytes_not_copied = 0;
>  
> -	bytes_not_copied = copy_to_user(buffer, buf, len);
>  	kfree(buf);
>  
>  	if (bytes_not_copied)
> -		return -EFAULT;
> +		return bytes_not_copied;
>  
>  	*ppos = len;
>  	return len;

For the code:

Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>

Thanks,
Olek