From:   Rameshkumar Sundaram <quic_ramess@quicinc.com>
To:     <johannes@sipsolutions.net>
CC:     <linux-wireless@vger.kernel.org>,
        Rameshkumar Sundaram <quic_ramess@quicinc.com>
Subject: [PATCH v2] wifi: mac80211: Allow NSS change only up to capability
Date:   Tue, 7 Feb 2023 17:11:46 +0530
Message-ID: <20230207114146.10567-1-quic_ramess@quicinc.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Stations can update bandwidth/NSS change in
VHT action frame with action type Operating Mode Notification.
(IEEE Std 802.11-2020 - 9.4.1.53 Operating Mode field)

For Operating Mode Notification, an RX NSS change to a value
greater than AP's maximum NSS should not be allowed.
During fuzz testing, by forcefully sending VHT Op. mode notif.
frames from STA with random rx_nss values, it is found that AP
accepts rx_nss values greater that APs maximum NSS instead of
discarding such NSS change.

Hence allow NSS change only up to maximum NSS that is negotiated
and capped to AP's capability during association.

Signed-off-by: Rameshkumar Sundaram <quic_ramess@quicinc.com>
---
Changes since v1:
- Updated commmit log
- Added comment to specify nss reset logic
---
 net/mac80211/vht.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/net/mac80211/vht.c b/net/mac80211/vht.c
index 803de5881485..c1250aa47808 100644
--- a/net/mac80211/vht.c
+++ b/net/mac80211/vht.c
@@ -625,7 +625,7 @@ u32 __ieee80211_vht_handle_opmode(struct ieee80211_sub_if_data *sdata,
 	enum ieee80211_sta_rx_bandwidth new_bw;
 	struct sta_opmode_info sta_opmode = {};
 	u32 changed = 0;
-	u8 nss;
+	u8 nss, cur_nss;
 
 	/* ignore - no support for BF yet */
 	if (opmode & IEEE80211_OPMODE_NOTIF_RX_NSS_TYPE_BF)
@@ -636,10 +636,25 @@ u32 __ieee80211_vht_handle_opmode(struct ieee80211_sub_if_data *sdata,
 	nss += 1;
 
 	if (link_sta->pub->rx_nss != nss) {
-		link_sta->pub->rx_nss = nss;
-		sta_opmode.rx_nss = nss;
-		changed |= IEEE80211_RC_NSS_CHANGED;
-		sta_opmode.changed |= STA_OPMODE_N_SS_CHANGED;
+		cur_nss = link_sta->pub->rx_nss;
+		/* Reset rx_nss and call ieee80211_sta_set_rx_nss() which
+		 * will set the same to max nss value calculated based on capability.
+		 */
+		link_sta->pub->rx_nss = 0;
+		ieee80211_sta_set_rx_nss(link_sta);
+		/* Do not allow an nss change to rx_nss greater than max_nss
+		 * negotiated and capped to APs capability during association.
+		 */
+		if (nss <= link_sta->pub->rx_nss) {
+			link_sta->pub->rx_nss = nss;
+			sta_opmode.rx_nss = nss;
+			changed |= IEEE80211_RC_NSS_CHANGED;
+			sta_opmode.changed |= STA_OPMODE_N_SS_CHANGED;
+		} else {
+			link_sta->pub->rx_nss = cur_nss;
+			pr_warn_ratelimited("Ignoring NSS change in VHT Operating Mode Notification from %pM with invalid nss %d",
+					    link_sta->pub->addr, nss);
+		}
 	}
 
 	switch (opmode & IEEE80211_OPMODE_NOTIF_CHANWIDTH_MASK) {

base-commit: 4ca69027691a0039279b64cfa0aa511d9c9fde59
-- 
2.17.1