linux-hardening - Re: [PATCH] dma-buf: Replace strlcpy() with strscpy()

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Date: Fri, 17 Nov 2023 10:50:21 -0800
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, Azeem Shaikh <azeemshaikh38@...il.com>, 
	linaro-mm-sig@...ts.linaro.org, linux-hardening@...r.kernel.org, 
	Christian König <christian.koenig@....com>, 
	linux-media@...r.kernel.org
Subject: Re: [PATCH] dma-buf: Replace strlcpy() with strscpy()

On Thu, Nov 16, 2023 at 11:14 AM Kees Cook <keescook@...omium.org> wrote:
>
> strlcpy() reads the entire source buffer first. This read may exceed
> the destination size limit. This is both inefficient and can lead
> to linear read overflows if a source string is not NUL-terminated[1].
> Additionally, it returns the size of the source string, not the
> resulting size of the destination string. In an effort to remove strlcpy()
> completely[2], replace strlcpy() here with strscpy().
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
> Link: https://github.com/KSPP/linux/issues/89 [2]
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: "Christian König" <christian.koenig@....com>
> Cc: Azeem Shaikh <azeemshaikh38@...il.com>
> Cc: linux-media@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linaro-mm-sig@...ts.linaro.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: T.J. Mercier <tjmercier@...gle.com>

strscpy returns -E2BIG when it truncates / force null-terminates which
would provide the wrong argument for dynamic_dname, but
dma_buf_set_name{_user} makes sure we have a null-terminated string of
the appropriate maximum size in dmabuf->name.