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Subject: Re: [PATCH 39/64] mac80211: Use memset_after() to clear tx status
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Kees Cook <keescook@chromium.org>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Keith Packard <keithpac@amazon.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
        netdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-staging@lists.linux.dev, linux-block@vger.kernel.org,
        linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com,
        linux-hardening@vger.kernel.org
Date:   Fri, 13 Aug 2021 20:19:36 +0200
In-Reply-To: <202108130907.FD09C6B@keescook>
References: <20210727205855.411487-1-keescook@chromium.org>
         <20210727205855.411487-40-keescook@chromium.org>
         <202107310852.551B66EE32@keescook>
         <bb01e784dddf6a297025981a2a000a4d3fdaf2ba.camel@sipsolutions.net>
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On Fri, 2021-08-13 at 09:08 -0700, Kees Cook wrote:
> > 
> > The common helper should also clear ack_signal, but that was broken by
> > commit e3e1a0bcb3f1 ("mac80211: reduce IEEE80211_TX_MAX_RATES"), because
> > that commit changed the order of the fields and updated carl9170 and p54
> > properly but not the common helper...
> 
> It looks like p54 actually uses the rates, which is why it does this
> manually. I can't see why carl9170 does this manually, though.

mac80211 also uses the rates later again on status reporting, it just
expects the # of attempts to be filled etc. I haven't looked at
carl9170, but I would expect it to do something there and do it
correctly, even though old it's a well-written driver and uses mac80211
rate control, so this would need to be correct for decent performance.

But I guess it could be that the helper could be used because the rates
were already handed to the firmware, and the code was just copy/pasted
from p54 (the drivers were, IIRC, developed by the same folks)

johannes