linux-hardening - Re: [PATCH v2] drm/i915: refactor deprecated strncpy

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Date: Wed, 20 Sep 2023 16:54:45 -0400
From: Rodrigo Vivi <rodrigo.vivi@...el.com>
To: Justin Stitt <justinstitt@...gle.com>
CC: Jani Nikula <jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin
	<tvrtko.ursulin@...ux.intel.com>, David Airlie <airlied@...il.com>, "Daniel
 Vetter" <daniel@...ll.ch>, <intel-gfx@...ts.freedesktop.org>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<linux-hardening@...r.kernel.org>
Subject: Re: [PATCH v2] drm/i915: refactor deprecated strncpy

On Tue, Sep 19, 2023 at 04:45:31AM +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` [2] due to the fact that it
> guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding. `ctx` is zero allocated and as such strncpy's
> NUL-padding behavior was strictly a performance hit which is now
> resolved.
> 
> 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@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
> Changes in v2:
> - drop the `... - 1` (thanks Kees)
> - Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-gpu-drm-i915-gem-selftests-mock_context-c-v1-1-c3f92df942e0@google.com
> ---


Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>

and pushing it right now to drm-intel-gt-next

>  drivers/gpu/drm/i915/gem/selftests/mock_context.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/selftests/mock_context.c b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> index 8ac6726ec16b..e199d7dbb876 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/mock_context.c
> @@ -36,7 +36,7 @@ mock_context(struct drm_i915_private *i915,
>  	if (name) {
>  		struct i915_ppgtt *ppgtt;
>  
> -		strncpy(ctx->name, name, sizeof(ctx->name) - 1);
> +		strscpy(ctx->name, name, sizeof(ctx->name));
>  
>  		ppgtt = mock_ppgtt(i915, name);
>  		if (!ppgtt)
> 
> ---
> base-commit: 3669558bdf354cd352be955ef2764cde6a9bf5ec
> change-id: 20230914-strncpy-drivers-gpu-drm-i915-gem-selftests-mock_context-c-980c8ecc9142
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
>