linux-kernel - Re: [PATCH v2] qed: replace uses of strncpy

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Message-ID: <202310121203.0415E3B@keescook>
Date:   Thu, 12 Oct 2023 12:03:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...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 v2] qed: replace uses of strncpy

On Thu, Oct 12, 2023 at 06:35:41PM +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.
> 
> This patch eliminates three uses of strncpy():
> 
> Firstly, `dest` is expected to be NUL-terminated which is evident by the
> manual setting of a NUL-byte at size - 1. For this use specifically,
> strscpy() is a viable replacement due to the fact that it guarantees
> NUL-termination on the destination buffer.
> 
> The next two cases should simply be memcpy() as the size of the src
> string is always 3 and the destination string just wants the first 3
> bytes changed.
> 
> To be clear, there are no buffer overread bugs in the current code as
> the sizes and offsets are carefully managed such that buffers are
> NUL-terminated. However, with these changes, the code is now more robust
> and less ambiguous (and hopefully easier to read).
> 
> 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
> Cc: Kees Cook <keescook@...omium.org>
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Yup, this looks good to me now. Thanks!

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

-- 
Kees Cook