linux-hardening - Re: [PATCH] dax: refactor deprecated strncpy

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Date:   Thu, 14 Sep 2023 20:40:51 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>, nvdimm@...ts.linux.dev,
        linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] dax: refactor deprecated strncpy

On Wed, Sep 13, 2023 at 01:10:24AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> `dax_id->dev_name` is expected to be NUL-terminated and has been zero-allocated.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on the destination buffer. Moreover, due to
> `dax_id` being zero-allocated the padding behavior of `strncpy` is not
> needed and a simple 1:1 replacement of strncpy -> strscpy should
> suffice.
> 
> 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 correct to me.

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

-- 
Kees Cook