linux-hardening - Re: [PATCH RFC kspp-next 0/3] compiler_types: add Endianness-dependent __counted_by

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Date: Mon, 18 Mar 2024 10:38:32 -0700
From: Kees Cook <keescook@...omium.org>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: linux-hardening@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Marco Elver <elver@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC kspp-next 0/3] compiler_types: add
 Endianness-dependent __counted_by_{le,be}

On Mon, Mar 18, 2024 at 02:03:51PM +0100, Alexander Lobakin wrote:
> Some structures contain flexible arrays at the end and the counter for
> them, but the counter has explicit Endianness and thus __counted_by()
> can't be used directly.
> 
> To increase test coverage for potential problems without breaking
> anything, introduce __counted_by_{le,be} defined depending on platform's
> Endianness to either __counted_by() when applicable or noop otherwise.
> The first user will be virtchnl2.h from idpf just as example with 9 flex
> structures having Little Endian counters.

Yeah, okay, that makes good sense. It'll give us as much coverage as we
can get until the compilers gain "expression" support for the
'counted_by' attribute.

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook