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

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Message-ID: <202312080921.112091F614@keescook>
Date:   Fri, 8 Dec 2023 09:21:51 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Shahed Shaikh <shshaikh@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        GR-Linux-NIC-Dev@...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] qlcnic: replace deprecated strncpy with strscpy

On Thu, Dec 07, 2023 at 09:42:22PM +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 fw_info->fw_file_name to be NUL-terminated based on its use
> within _request_firmware_prepare() wherein `name` refers to it:
> |       if (firmware_request_builtin_buf(firmware, name, dbuf, size)) {
> |               dev_dbg(device, "using built-in %s\n", name);
> |               return 0; /* assigned */
> |       }
> ... and with firmware_request_builtin() also via `name`:
> |       if (strcmp(name, b_fw->name) == 0) {
> 
> There is no evidence that NUL-padding is required.
> 
> Additionally replace size macro (QLC_FW_FILE_NAME_LEN) with
> sizeof(fw_info->fw_file_name) to more directly tie the maximum buffer
> size to the destination buffer:
> 
> 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>

Thanks for the refresh!

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

-- 
Kees Cook