netdev - Re: [PATCH] overflow: Change DEFINE_FLEX to take __counted

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Date: Tue, 5 Mar 2024 21:25:51 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Kees Cook <keescook@...omium.org>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>,
 Tony Nguyen <anthony.l.nguyen@...el.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
 linux-hardening@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] overflow: Change DEFINE_FLEX to take __counted_by member

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@...omium.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