linux-kernel - Re: [PATCH] cavium/liquidio: replace deprecated strncpy with strscpy

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Message-ID: <202310051621.3893B1EA4@keescook>
Date:   Thu, 5 Oct 2023 16:22:10 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Derek Chickles <dchickles@...vell.com>,
        Satanand Burla <sburla@...vell.com>,
        Felix Manlunas <fmanlunas@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] cavium/liquidio: replace deprecated strncpy with strscpy

On Thu, Oct 05, 2023 at 10:52:34PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> We expect `app_name` to be NUL-terminated:
> 	dev_info(&oct->pci_dev->dev,
> 		 "Running %s (%llu Hz)\n",
> 		 app_name, CVM_CAST64(cs->corefreq));
> ... and it seems NUL-padding is not required, let's opt for strscpy().
> 
> For `oct->boardinfo.name/serial_number` let's opt for strscpy() as well
> since it is expected to be NUL-terminated and does not require
> NUL-padding as `oct` is zero-initialized in octeon_device.c +707:
> |       buf = vzalloc(size);
> |       if (!buf)
> |       	return NULL;
> |
> |       oct = (struct octeon_device *)buf;
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
> Note: build-tested only.
> ---
>  drivers/net/ethernet/cavium/liquidio/octeon_device.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/octeon_device.c b/drivers/net/ethernet/cavium/liquidio/octeon_device.c
> index 364f4f912dc2..6b6cb73482d7 100644
> --- a/drivers/net/ethernet/cavium/liquidio/octeon_device.c
> +++ b/drivers/net/ethernet/cavium/liquidio/octeon_device.c
> @@ -1217,10 +1217,10 @@ int octeon_core_drv_init(struct octeon_recv_info *recv_info, void *buf)
>  		goto core_drv_init_err;
>  	}
>  
> -	strncpy(app_name,
> +	strscpy(app_name,
>  		get_oct_app_string(
>  		(u32)recv_pkt->rh.r_core_drv_init.app_mode),
> -		sizeof(app_name) - 1);
> +		sizeof(app_name));

Direct replacement, good.

>  	oct->app_mode = (u32)recv_pkt->rh.r_core_drv_init.app_mode;
>  	if (recv_pkt->rh.r_core_drv_init.app_mode == CVM_DRV_NIC_APP) {
>  		oct->fw_info.max_nic_ports =
> @@ -1257,9 +1257,10 @@ int octeon_core_drv_init(struct octeon_recv_info *recv_info, void *buf)
>  	memcpy(cs, get_rbd(
>  	       recv_pkt->buffer_ptr[0]) + OCT_DROQ_INFO_SIZE, sizeof(*cs));
>  
> -	strncpy(oct->boardinfo.name, cs->boardname, OCT_BOARD_NAME);
> -	strncpy(oct->boardinfo.serial_number, cs->board_serial_number,
> -		OCT_SERIAL_LEN);
> +	strscpy(oct->boardinfo.name, cs->boardname,
> +		    sizeof(oct->boardinfo.name));
> +	strscpy(oct->boardinfo.serial_number, cs->board_serial_number,
> +		    sizeof(oct->boardinfo.serial_number));

struct octeon_board_info {
        char name[OCT_BOARD_NAME];
        char serial_number[OCT_SERIAL_LEN];

Good, sizeof()s match.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook