linux-hardening - Re: [PATCH v2] drm/etnaviv: refactor deprecated strncpy

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Date: Fri, 6 Oct 2023 13:23:56 -0700
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Lucas Stach <l.stach@...gutronix.de>,
	Russell King <linux+etnaviv@...linux.org.uk>,
	Christian Gmeiner <christian.gmeiner@...il.com>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	etnaviv@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
	Bo YU <tsu.yubo@...il.com>
Subject: Re: [PATCH v2] drm/etnaviv: refactor deprecated strncpy

On Mon, Sep 18, 2023 at 01:34:08PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> A suitable replacement is `strscpy_pad` due to the fact that it
> guarantees NUL-termination on the destination buffer whilst maintaining
> the NUL-padding behavior that strncpy provides.

Friend ping. Who can pick this change up?

Thanks!

-Kees

> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Cc: Bo YU <tsu.yubo@...il.com>
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
> Changes in v2:
> - use strscpy_pad (thanks Kees)
> - Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-gpu-drm-etnaviv-etnaviv_perfmon-c-v1-1-3adc2d9bfc52@google.com
> ---
> Similar to [2] which was never picked up. Let's prefer strscpy_pad to strlcpy, though
> 
> [2]: https://lore.kernel.org/all/20190328080918.9290-1-tsu.yubo@gmail.com/
> ---
>  drivers/gpu/drm/etnaviv/etnaviv_perfmon.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> index bafdfe49c1d8..dc9dea664a28 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> @@ -511,7 +511,7 @@ int etnaviv_pm_query_dom(struct etnaviv_gpu *gpu,
>  
>  	domain->id = domain->iter;
>  	domain->nr_signals = dom->nr_signals;
> -	strncpy(domain->name, dom->name, sizeof(domain->name));
> +	strscpy_pad(domain->name, dom->name, sizeof(domain->name));
>  
>  	domain->iter++;
>  	if (domain->iter == nr_domains)
> @@ -540,7 +540,7 @@ int etnaviv_pm_query_sig(struct etnaviv_gpu *gpu,
>  	sig = &dom->signal[signal->iter];
>  
>  	signal->id = signal->iter;
> -	strncpy(signal->name, sig->name, sizeof(signal->name));
> +	strscpy_pad(signal->name, sig->name, sizeof(signal->name));
>  
>  	signal->iter++;
>  	if (signal->iter == dom->nr_signals)
> 
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-gpu-drm-etnaviv-etnaviv_perfmon-c-dd095491dfde
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
> 

-- 
Kees Cook