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

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Message-ID: <202310051617.3C4A40C5@keescook>
Date:   Thu, 5 Oct 2023 16:18:26 -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] liquidio: replace deprecated strncpy with strscpy

On Thu, Oct 05, 2023 at 09:55:06PM +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.
> 
> NUL-padding is not required as rep_cfg is memset to 0:
> |       memset(&rep_cfg, 0, sizeof(rep_cfg));
> 
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> 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/lio_vf_rep.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c b/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c
> index 600de587d7a9..aa6c0dfb6f1c 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c
> @@ -638,7 +638,8 @@ lio_vf_rep_netdev_event(struct notifier_block *nb,
>  	memset(&rep_cfg, 0, sizeof(rep_cfg));
>  	rep_cfg.req_type = LIO_VF_REP_REQ_DEVNAME;
>  	rep_cfg.ifidx = vf_rep->ifidx;
> -	strncpy(rep_cfg.rep_name.name, ndev->name, LIO_IF_NAME_SIZE);
> +	strscpy(rep_cfg.rep_name.name, ndev->name,
> +		sizeof(rep_cfg.rep_name.name));

struct lio_vf_rep_req {
	...
        union {
                struct lio_vf_rep_name {
                        char name[LIO_IF_NAME_SIZE];
                } rep_name;

Yup, sizeof(rep_cfg.rep_name.name) == LIO_IF_NAME_SIZE.

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

-- 
Kees Cook