Re: [PATCH] overflow: Change DEFINE_FLEX to take __counted_by member

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Kees Cook <keescook@chromium.org>,
	Przemek Kitszel <przemyslaw.kitszel@intel.com>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Tony Nguyen <anthony.l.nguyen@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
	linux-hardening@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] overflow: Change DEFINE_FLEX to take __counted_by member
Date: Tue, 5 Mar 2024 21:25:51 -0600	[thread overview]
Message-ID: <9c2990f0-7407-49c6-9e3a-b92de82ea437@embeddedor.com> (raw)
In-Reply-To: <20240306010746.work.678-kees@kernel.org>

On 05/03/24 19:07, Kees Cook wrote:
> The norm should be flexible array structures with __counted_by
> annotations, so DEFINE_FLEX() is updated to expect that. Rename
> the non-annotated version to DEFINE_RAW_FLEX(), and update the few
> existing users. Additionally add self-tests to validate syntax and
> size calculations.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---

[..]

> +/**
> + * DEFINE_FLEX() - Define an on-stack instance of structure with a trailing
> + * flexible array member.
> + *
> + * @TYPE: structure type name, including "struct" keyword.
> + * @NAME: Name for a variable to define.
> + * @COUNTER: Name of the __counted_by member.
> + * @MEMBER: Name of the array member.
> + * @COUNT: Number of elements in the array; must be compile-time const.
> + *
> + * Define a zeroed, on-stack, instance of @TYPE structure with a trailing
> + * flexible array member.
> + * Use __struct_size(@NAME) to get compile-time size of it afterwards.
> + */
> +#define DEFINE_FLEX(TYPE, NAME, COUNTER, MEMBER, COUNT)	\

Probably, swapping COUNTER and MEMBER is better?

	DEFINE_FLEX(TYPE, NAME, MEMBER, COUNTER, COUNT)

Thanks
--
Gustavo