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Date: Thu, 28 Mar 2024 21:06:28 -0700
From: Kees Cook <keescook@chromium.org>
To: Justin Stitt <justinstitt@google.com>
Cc: Timur Tabi <timur@kernel.org>, Helge Deller <deller@gmx.de>,
	linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] video: fbdev: fsl-diu-fb: replace deprecated strncpy
 with strscpy_pad
Message-ID: <202403282106.4D3757F@keescook>
References: <20240320-strncpy-drivers-video-fbdev-fsl-diu-fb-c-v1-1-3cd3c012fa8c@google.com>
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In-Reply-To: <20240320-strncpy-drivers-video-fbdev-fsl-diu-fb-c-v1-1-3cd3c012fa8c@google.com>

On Wed, Mar 20, 2024 at 10:48:50PM +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.
> 
> A better alternative is strscpy() as it guarantees NUL-termination on
> the destination buffer.
> 
> Since we are eventually copying over to userspace, let's ensure we
> NUL-pad the destination buffer by using the pad variant of strscpy.
> - core/fb_chrdev.c:
> 234 |	err = copy_to_user(&fix32->id, &fix->id, sizeof(fix32->id));
> 
> Furthermore, we can use the new 2-argument variants of strscpy() and
> strscpy_pad() introduced by Commit e6584c3964f2f ("string: Allow
> 2-argument strscpy()") to simplify the syntax even more.
> 
> 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 <justinstitt@google.com>

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

-- 
Kees Cook