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From:   Kees Cook <keescook@chromium.org>
To:     linux-hardening@vger.kernel.org
Cc:     Kees Cook <keescook@chromium.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
Subject: [PATCH 39/64] mac80211: Use memset_after() to clear tx status
Date:   Tue, 27 Jul 2021 13:58:30 -0700
Message-Id: <20210727205855.411487-40-keescook@chromium.org>
In-Reply-To: <20210727205855.411487-1-keescook@chromium.org>
References: <20210727205855.411487-1-keescook@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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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.

Note that the common helper, ieee80211_tx_info_clear_status(), does NOT
clear ack_signal, but the open-coded versions do. All three perform
checks that the ack_signal position hasn't changed, though.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
Should these each be clearing the same region? Because they're currently not.
---
 drivers/net/wireless/ath/carl9170/tx.c   | 4 +---
 drivers/net/wireless/intersil/p54/txrx.c | 4 +---
 include/net/mac80211.h                   | 4 +---
 3 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/net/wireless/ath/carl9170/tx.c b/drivers/net/wireless/ath/carl9170/tx.c
index 88444fe6d1c6..6d2115639434 100644
--- a/drivers/net/wireless/ath/carl9170/tx.c
+++ b/drivers/net/wireless/ath/carl9170/tx.c
@@ -278,9 +278,7 @@ static void carl9170_tx_release(struct kref *ref)
 	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));
+	memset_after(&txinfo->status, 0, rates);
 
 	if (atomic_read(&ar->tx_total_queued))
 		ar->tx_schedule = true;
diff --git a/drivers/net/wireless/intersil/p54/txrx.c b/drivers/net/wireless/intersil/p54/txrx.c
index 873fea59894f..f71b355f8583 100644
--- a/drivers/net/wireless/intersil/p54/txrx.c
+++ b/drivers/net/wireless/intersil/p54/txrx.c
@@ -431,9 +431,7 @@ static void p54_rx_frame_sent(struct p54_common *priv, struct sk_buff *skb)
 	 * Clear manually, ieee80211_tx_info_clear_status would
 	 * clear the counts too and we need them.
 	 */
-	memset(&info->status.ack_signal, 0,
-	       sizeof(struct ieee80211_tx_info) -
-	       offsetof(struct ieee80211_tx_info, status.ack_signal));
+	memset_after(&info->status, 0, rates);
 	BUILD_BUG_ON(offsetof(struct ieee80211_tx_info,
 			      status.ack_signal) != 20);
 
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index d8a1d09a2141..7abc1427aa8c 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1200,9 +1200,7 @@ ieee80211_tx_info_clear_status(struct ieee80211_tx_info *info)
 
 	BUILD_BUG_ON(
 	    offsetof(struct ieee80211_tx_info, status.ack_signal) != 20);
-	memset(&info->status.ampdu_ack_len, 0,
-	       sizeof(struct ieee80211_tx_info) -
-	       offsetof(struct ieee80211_tx_info, status.ampdu_ack_len));
+	memset_after(&info->status, 0, ack_signal);
 }
 
 
-- 
2.30.2