linux-hardening - Re: [PATCH] video/hdmi: prefer length specifier in format over string copying

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Date: Thu, 28 Mar 2024 21:04:50 -0700
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Helge Deller <deller@....de>, linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] video/hdmi: prefer length specifier in format over
 string copying

On Wed, Mar 20, 2024 at 11:22:02PM +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.
> 
> It looks like the main use of strncpy() here is to limit the amount of
> bytes printed from hdmi_log() by using a tmp buffer and limiting the
> number of bytes copied. Really, we should use the %.<len>s format
> qualifier to achieve this.
> 
> 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
> 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>

-- 
Kees Cook