linux-hardening - Re: [PATCH] accel/habanalabs: refactor deprecated strncpy to strscpy

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Date:   Fri, 25 Aug 2023 15:13:35 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Oded Gabbay <ogabbay@...nel.org>, Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] accel/habanalabs: refactor deprecated strncpy to
 strscpy_pad

On Fri, Aug 25, 2023 at 10:09:51PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We see that `prop->cpucp_info.card_name` is supposed to be
> NUL-terminated based on its usage within `__hwmon_device_register()`
> (wherein it's called "name"):
> |	if (name && (!strlen(name) || strpbrk(name, "-* \t\n")))
> |		dev_warn(dev,
> |			 "hwmon: '%s' is not a valid name attribute, please fix\n",
> |			 name);
> 
> A suitable replacement is `strscpy_pad` [2] due to the fact that it
> guarantees both NUL-termination and NUL-padding on its destination
> buffer.
> 
> NUL-padding on `prop->cpucp_info.card_name` is not strictly necessary as
> `hdev->prop` is explicitly zero-initialized but should be used
> regardless as it gets copied out to userspace directly -- as per Kees' suggestion.
> 
> Link: 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 consolidation and refresh. :)

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

-- 
Kees Cook