Re: [PATCH] sctp: prefer struct_size over open coded arithmetic

From: Erick Archer <erick.archer@outlook.com>
To: Kees Cook <keescook@chromium.org>, Xin Long <lucien.xin@gmail.com>
Cc: Erick Archer <erick.archer@outlook.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@gmail.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>,
	Justin Stitt <justinstitt@google.com>,
	linux-sctp@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] sctp: prefer struct_size over open coded arithmetic
Date: Wed, 1 May 2024 18:37:18 +0200	[thread overview]
Message-ID: <AS8PR02MB7237FFA530C63CD23BCAED378B192@AS8PR02MB7237.eurprd02.prod.outlook.com> (raw)
In-Reply-To: <202404291044.E9A6A13@keescook>

Hi Kees and Xin,

On Mon, Apr 29, 2024 at 10:45:20AM -0700, Kees Cook wrote:
> On Sat, Apr 27, 2024 at 07:23:36PM +0200, Erick Archer wrote:
> > This is an effort to get rid of all multiplications from allocation
> > functions in order to prevent integer overflows [1][2].
> > 
> > As the "ids" variable is a pointer to "struct sctp_assoc_ids" and this
> > structure ends in a flexible array:
> > 
> > struct sctp_assoc_ids {
>         __u32           gaids_number_of_ids;
> > 	sctp_assoc_t	gaids_assoc_id[];
> > };
> 
> This could gain __counted_by:
> 
> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> index b7d91d4cf0db..836173e73401 100644
> --- a/include/uapi/linux/sctp.h
> +++ b/include/uapi/linux/sctp.h
> @@ -1007,7 +1007,7 @@ enum sctp_sstat_state {
>   */
>  struct sctp_assoc_ids {
>  	__u32		gaids_number_of_ids;
> -	sctp_assoc_t	gaids_assoc_id[];
> +	sctp_assoc_t	gaids_assoc_id[] __counted_by(gaids_number_of_ids);
>  };
>  

Since this patch has been applied to the linux-next tree, I will send an
incremental one.

Thanks Kees and Xin for the review.

Regards,
Erick