linux-hardening - Re: [PATCH] mac80211: Use memset

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Date:   Sat, 20 Nov 2021 16:17:33 +0100
From:   Christian Lamparter <chunkeey@...il.com>
To:     Kees Cook <keescook@...omium.org>,
        Johannes Berg <johannes@...solutions.net>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Christian Lamparter <chunkeey@...glemail.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] mac80211: Use memset_after() to clear tx status

On 18/11/2021 21:38, 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.
> 
> Use memset_after() so memset() doesn't get confused about writing
> beyond the destination member that is intended to be the starting point
> of zeroing through the end of the struct.
> 
> Additionally fix the common helper, ieee80211_tx_info_clear_status(),
> which was not clearing ack_signal, but the open-coded versions
> did. Johannes Berg points out this bug was introduced by commit
> e3e1a0bcb3f1 ("mac80211: reduce IEEE80211_TX_MAX_RATES") but was harmless.
> 
> Also drops the associated unneeded BUILD_BUG_ON()s, and adds a note to
> carl9170 about usage.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
Tested-by: Christian Lamparter <chunkeey@...il.com> [both CARL9170+P54USB on real HW]