netdev - Re: [PATCH iwl-next] i40e: Use correct buffer size

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Date: Wed, 15 Nov 2023 16:39:27 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Kunwu Chan <chentao@...inos.cn>
CC: <horms@...nel.org>, <anthony.l.nguyen@...el.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <intel-wired-lan@...ts.osuosl.org>,
	<jeffrey.t.kirsher@...el.com>, <jesse.brandeburg@...el.com>,
	<kuba@...nel.org>, <kunwu.chan@...mail.com>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <pabeni@...hat.com>, <shannon.nelson@....com>
Subject: Re: [PATCH iwl-next] i40e: Use correct buffer size

From: Kunwu Chan <chentao@...inos.cn>
Date: Wed, 15 Nov 2023 11:14:44 +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, fix it.
> 
> Signed-off-by: Kunwu Chan <chentao@...inos.cn>
> Suggested-by: Simon Horman <horms@...nel.org>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> index 999c9708def5..e3b939c67cfe 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> @@ -72,7 +72,7 @@ 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;
> +	int buf_size = IFNAMSIZ + sizeof(i40e_dbg_command_buf) + 4;

Reverse Christmas Tree style? Should be the first one in the declaration
list.

>  	char *buf;
>  	int len;

You can fix it in a different way. Given that there's a kzalloc() either
way, why not allocate the precise required amount of bytes by using
kasprintf() instead of kzalloc() + snprintf()? You wouldn't need to
calculate any buffer sizes etc. this way.

Thanks,
Olek