linux-kernel - Re: [PATCH v2] wifi: ipw2x00: replace deprecated strncpy with strscpy

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Date:   Mon, 23 Oct 2023 17:26:49 +0000 (UTC)
From:   Kalle Valo <kvalo@...nel.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Stanislav Yakovlev <stas.yakovlev@...il.com>,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: Re: [PATCH v2] wifi: ipw2x00: replace deprecated strncpy with
 strscpy_pad

Justin Stitt <justinstitt@...gle.com> 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.
> 
> `extra` is intended to be NUL-terminated which is evident by the manual
> assignment of a NUL-byte as well as its immediate usage with strlen().
> 
> Moreover, many of these getters and setters are NUL-padding buffers with
> memset():
> 2439  |	memset(&tx_power, 0, sizeof(tx_power));
> 9998  | memset(sys_config, 0, sizeof(struct ipw_sys_config));
> 10084 | memset(tfd, 0, sizeof(*tfd));
> 10261 | memset(&dummystats, 0, sizeof(dummystats));
> ... let's maintain this behavior and NUL-pad our destination buffer.
> 
> Considering the above, a suitable replacement is `strscpy_pad` due to
> the fact that it guarantees both NUL-termination and NUL-padding on the
> destination buffer.
> 
> To be clear, there is no bug in the current implementation as
> MAX_WX_STRING is much larger than the size of the string literals being
> copied from. Also, strncpy() does NUL-pad the destination buffer and
> using strscpy_pad() simply matches that behavior. All in all, there
> should be no functional change but we are one step closer to eliminating
> usage of strncpy().
> 
> Do note that we cannot use the more idiomatic strscpy invocation of
> (dest, src, sizeof(dest)) as the destination buffer cannot have its size
> determined at compile time. So, let's stick with (dest, src, LEN).
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>

Patch applied to wireless-next.git, thanks.

8890b9bca38f wifi: ipw2x00: replace deprecated strncpy with strscpy_pad

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20231017-strncpy-drivers-net-wireless-intel-ipw2x00-ipw2200-c-v2-1-465e10dc817c@google.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches