linux-hardening - Re: [PATCH] ethtool: stats: Use struct

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Message-ID: <20211119062724.731da986@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Fri, 19 Nov 2021 06:27:24 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Ido Schimmel <idosch@...dia.com>,
        YueHaibing <yuehaibing@...wei.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ethtool: stats: Use struct_group() to clear all stats
 at once

On Thu, 18 Nov 2021 12:34:56 -0800 Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
> 
> Add struct_group() to mark region of struct stats_reply_data that should
> be initialized, which can now be done in a single memset() call.

No objection to the patch, but the commit message does not work 
for this one ;)

> diff --git a/net/ethtool/stats.c b/net/ethtool/stats.c
> index ec07f5765e03..a20e0a24ff61 100644
> --- a/net/ethtool/stats.c
> +++ b/net/ethtool/stats.c
> @@ -14,10 +14,12 @@ struct stats_req_info {
>  
>  struct stats_reply_data {
>  	struct ethnl_reply_data		base;
> -	struct ethtool_eth_phy_stats	phy_stats;
> -	struct ethtool_eth_mac_stats	mac_stats;
> -	struct ethtool_eth_ctrl_stats	ctrl_stats;
> -	struct ethtool_rmon_stats	rmon_stats;
> +	struct_group(stats,
> +		struct ethtool_eth_phy_stats	phy_stats;
> +		struct ethtool_eth_mac_stats	mac_stats;
> +		struct ethtool_eth_ctrl_stats	ctrl_stats;
> +		struct ethtool_rmon_stats	rmon_stats;
> +	);
>  	const struct ethtool_rmon_hist_range	*rmon_ranges;
>  };
>  
> @@ -117,10 +119,7 @@ static int stats_prepare_data(const struct ethnl_req_info *req_base,
>  	/* Mark all stats as unset (see ETHTOOL_STAT_NOT_SET) to prevent them
>  	 * from being reported to user space in case driver did not set them.
>  	 */
> -	memset(&data->phy_stats, 0xff, sizeof(data->phy_stats));
> -	memset(&data->mac_stats, 0xff, sizeof(data->mac_stats));
> -	memset(&data->ctrl_stats, 0xff, sizeof(data->ctrl_stats));
> -	memset(&data->rmon_stats, 0xff, sizeof(data->rmon_stats));
> +	memset(&data->stats, 0xff, sizeof(data->stats));
>  
>  	if (test_bit(ETHTOOL_STATS_ETH_PHY, req_info->stat_mask) &&
>  	    dev->ethtool_ops->get_eth_phy_stats)