linux-kernel - Re: [PATCH] c2port: replace deprecated strncpy with strscpy

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Message-Id: <b70fa1d5-7f38-4511-ad2a-abe1b1ad5992@app.fastmail.com>
Date:   Wed, 27 Sep 2023 07:49:56 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Justin Stitt" <justinstitt@...gle.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] c2port: replace deprecated strncpy with strscpy

On Wed, Sep 27, 2023, at 07:20, 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 `c2dev->name` to be NUL-terminated based on its usage with
> format strings:
> |       dev_info(c2dev->dev, "C2 port %s removed\n", c2dev->name);
>
> Moreover, NUL-padding is _not_ required as c2dev is zero-allocated:
> |       c2dev = kzalloc(sizeof(struct c2port_device), GFP_KERNEL);
>
> 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.
>
> Let's also drop `C2PORT_NAME_LEN - 1` for `sizeof(dest)` which is more
> idiomatic strscpy usage.
>
> 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>

Reviewed-by: Arnd Bergmann <arnd@...db.de>