From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9554E208D7 for ; Mon, 23 Oct 2023 17:29:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FVgWfTu2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4C05C433BF; Mon, 23 Oct 2023 17:29:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698082144; bh=QHFYOWlkGzWzBm8/TDgaH/NxaV2cslJrLINWwlJQA/s=; h=Subject:From:In-Reply-To:References:To:Cc:Date:From; b=FVgWfTu2X8tsb3prDb290Ls4nIJjC2E6e+STuJrtghR8sn4A7zuJHXf7ReOr7uRv9 X3vbQv5lLeOSahlR7Q0Uj6EQiFbDa7hbehu/4xm7jPh8xDXnKVgbO8Sbu5voHC9keB EdxUfDnK9RwbuZ/OmB0SSicqHWPu/CiDyPCWTd1pknVzWmra/gjOAW9JZ9B09Q9EgS PGJIpp9kqg5jS6OYM6k1RcRBTHhxtxrrWmEPo/DZ8SFeBrL7+3g2cVTmTXJ4LGRF4G FFpCqxIKSgvx6YfwS8Fy0h0HoG5xSVkkLb3Fx8Tbj1J8hx4kvIlHDBu6PJNW7cMbj9 uYIcOimdXRO/Q== Content-Type: text/plain; charset="utf-8" Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [PATCH v2] wifi: wl18xx: replace deprecated strncpy with strscpy From: Kalle Valo In-Reply-To: <20231018-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v2-1-ab828a491ce5@google.com> References: <20231018-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v2-1-ab828a491ce5@google.com> To: Justin Stitt Cc: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt User-Agent: pwcli/0.1.1-git (https://github.com/kvalo/pwcli/) Python/3.11.2 Message-ID: <169808214096.695306.16867371927362677555.kvalo@kernel.org> Date: Mon, 23 Oct 2023 17:29:02 +0000 (UTC) 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. > > wl->chip.phy_fw_ver_str is obviously intended to be NUL-terminated by > the deliberate comment telling us as much. Furthermore, its only use is > drivers/net/wireless/ti/wlcore/debugfs.c shows us it should be > NUL-terminated since its used in scnprintf: > 492 | DRIVER_STATE_PRINT_STR(chip.phy_fw_ver_str); > which is defined as: > | #define DRIVER_STATE_PRINT_STR(x) DRIVER_STATE_PRINT(x, "%s") > ... > | #define DRIVER_STATE_PRINT(x, fmt) \ > | (res += scnprintf(buf + res, DRIVER_STATE_BUF_LEN - res,\ > | #x " = " fmt "\n", wl->x)) > > We can also see that NUL-padding is not required. > > 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. > > The very fact that a plain-english comment had to be made alongside a > manual NUL-byte assignment for such a simple purpose shows why strncpy > is faulty. It has non-obvious behavior that has to be clarified every > time it is used (and if it isn't then the reader suffers). > > 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@vger.kernel.org > Signed-off-by: Justin Stitt > Reviewed-by: Kees Cook Patch applied to wireless-next.git, thanks. fb329e8b1d88 wifi: wl18xx: replace deprecated strncpy with strscpy -- https://patchwork.kernel.org/project/linux-wireless/patch/20231018-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v2-1-ab828a491ce5@google.com/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches