linux-kernel - Re: [PATCH 1/4][next] i40e: Replace one-element array with flex-array member in struct i40e_package

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Message-ID: <ZMpz3re48diGmG/Z@kernel.org>
Date:   Wed, 2 Aug 2023 17:18:54 +0200
From:   Simon Horman <horms@...nel.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
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>, netdev@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/4][next] i40e: Replace one-element array with
 flex-array member in struct i40e_package_header

On Tue, Aug 01, 2023 at 11:05:31PM -0600, Gustavo A. R. Silva wrote:
> One-element and zero-length arrays are deprecated. So, replace
> one-element array in struct i40e_package_header with flexible-array
> member.
> 
> The `+ sizeof(u32)` adjustments ensure that there are no differences
> in binary output.
> 
> Link: https://github.com/KSPP/linux/issues/335
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_ddp.c  | 4 ++--
>  drivers/net/ethernet/intel/i40e/i40e_type.h | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_ddp.c b/drivers/net/ethernet/intel/i40e/i40e_ddp.c
> index 7e8183762fd9..0db6f5e3cfcc 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_ddp.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_ddp.c
> @@ -220,7 +220,7 @@ static bool i40e_ddp_is_pkg_hdr_valid(struct net_device *netdev,
>  		netdev_err(netdev, "Invalid DDP profile - size is bigger than 4G");
>  		return false;
>  	}
> -	if (size < (sizeof(struct i40e_package_header) +
> +	if (size < (sizeof(struct i40e_package_header) + sizeof(u32) +

Hi Gustavo,

would it make more sense to use struct_size() here?

>  		sizeof(struct i40e_metadata_segment) + sizeof(u32) * 2)) {
>  		netdev_err(netdev, "Invalid DDP profile - size is too small.");
>  		return false;
> @@ -281,7 +281,7 @@ int i40e_ddp_load(struct net_device *netdev, const u8 *data, size_t size,
>  	if (!i40e_ddp_is_pkg_hdr_valid(netdev, pkg_hdr, size))
>  		return -EINVAL;
>  
> -	if (size < (sizeof(struct i40e_package_header) +
> +	if (size < (sizeof(struct i40e_package_header) + sizeof(u32) +
>  		    sizeof(struct i40e_metadata_segment) + sizeof(u32) * 2)) {
>  		netdev_err(netdev, "Invalid DDP recipe size.");
>  		return -EINVAL;
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_type.h b/drivers/net/ethernet/intel/i40e/i40e_type.h
> index 388c3d36d96a..c3d5fe12059a 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_type.h
> +++ b/drivers/net/ethernet/intel/i40e/i40e_type.h
> @@ -1456,7 +1456,7 @@ struct i40e_ddp_version {
>  struct i40e_package_header {
>  	struct i40e_ddp_version version;
>  	u32 segment_count;
> -	u32 segment_offset[1];
> +	u32 segment_offset[];
>  };
>  
>  /* Generic segment header */
> -- 
> 2.34.1
> 
>