linux-hardening - Re: [PATCH v2 44/63] mac80211: Use memset

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Date:   Wed, 18 Aug 2021 09:08:52 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        dri-devel@...ts.freedesktop.org, linux-staging@...ts.linux.dev,
        linux-block@...r.kernel.org, linux-kbuild@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 44/63] mac80211: Use memset_after() to clear tx status

On Tue, 2021-08-17 at 23:05 -0700, Kees Cook wrote:
> 
> @@ -275,12 +275,11 @@ static void carl9170_tx_release(struct kref *ref)
>  	if (WARN_ON_ONCE(!ar))
>  		return;
>  
> 
> 
> 
> -	BUILD_BUG_ON(
> -	    offsetof(struct ieee80211_tx_info, status.ack_signal) != 20);
> -
> -	memset(&txinfo->status.ack_signal, 0,
> -	       sizeof(struct ieee80211_tx_info) -
> -	       offsetof(struct ieee80211_tx_info, status.ack_signal));
> +	/*
> +	 * Should this call ieee80211_tx_info_clear_status() instead of clearing
> +	 * manually? txinfo->status.rates do not seem to be used here.
> +	 */

Since you insist, I went digging :)

It should not, carl9170_tx_fill_rateinfo() has filled the rate
information before we get to this point.

johannes