linux-hardening - Re: [PATCH] comedi: Annotate struct comedi_lrange with __counted

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Message-ID: <935d0577-4a6a-eb84-6ae0-f1efa4352b5b@embeddedor.com>
Date: Sun, 1 Oct 2023 08:43:41 +0200
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 Ian Abbott <abbotti@....co.uk>,
 H Hartley Sweeten <hsweeten@...ionengravers.com>,
 Kees Cook <keescook@...omium.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>
Cc: linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 linux-hardening@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] comedi: Annotate struct comedi_lrange with __counted_by

On 9/30/23 11:14, Christophe JAILLET wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
-- 
Gustavo

> ---
> This patch is part of a work done in parallel of what is currently worked
> on by Kees Cook.
> 
> My patches are only related to corner cases that do NOT match the
> semantic of his Coccinelle script[1].
> 
> In this case, it is been spotted because of comedi_alloc_spriv().
> All other usages of struct comedi_lrange seem to be static definition of
> the structure that explicitly set the .length field.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> ---
>   include/linux/comedi/comedidev.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/comedi/comedidev.h b/include/linux/comedi/comedidev.h
> index 0a1150900ef3..c08416a7364b 100644
> --- a/include/linux/comedi/comedidev.h
> +++ b/include/linux/comedi/comedidev.h
> @@ -633,7 +633,7 @@ extern const struct comedi_lrange range_unknown;
>    */
>   struct comedi_lrange {
>   	int length;
> -	struct comedi_krange range[];
> +	struct comedi_krange range[] __counted_by(length);
>   };
>   
>   /**