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

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Message-ID: <202310042157.D314C6D7EF@keescook>
Date:   Wed, 4 Oct 2023 21:57:38 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Chris Snook <chris.snook@...il.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] net: atheros: replace deprecated strncpy with strscpy

On Thu, Oct 05, 2023 at 01:29:45AM +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 netdev->name to be NUL-terminated based on its use with format
> strings and dev_info():
> |     dev_info(&adapter->pdev->dev,
> |             "%s link is up %d Mbps %s\n",
> |             netdev->name, adapter->link_speed,
> |             adapter->link_duplex == FULL_DUPLEX ?
> |             "full duplex" : "half duplex");
> 
> Furthermore, NUL-padding is not required as netdev is already
> zero-initialized through alloc_etherdev().
> 
> Considering the above, 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>

Looks right; destination length correctly updated.

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

-- 
Kees Cook