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From:   Hans de Goede <hdegoede@redhat.com>
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     Hans de Goede <hdegoede@redhat.com>,
        Helmut Schaa <helmut.schaa@googlemail.com>,
        linux-wireless@vger.kernel.org,
        Markus Theil <markus.theil@tu-ilmenau.de>,
        Stanislaw Gruszka <stf_xl@wp.pl>
Subject: [PATCH] mac80211: Fix regression caused by 'enable QoS support for nl80211 ctrl port'
Date:   Sun, 18 Sep 2022 21:20:52 +0200
Message-Id: <20220918192052.443529-1-hdegoede@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Commit 10cb8e617560 ("mac80211: enable QoS support for nl80211 ctrl port")
changed ieee80211_tx_control_port() to aways call
__ieee80211_select_queue() without checking local->hw.queues.

__ieee80211_select_queue() returns a queue-id between 0 and 3, which means
that now ieee80211_tx_control_port() may end up setting the queue-mapping
for a skb to a value higher then local->hw.queues if local->hw.queues
is less then 4.

Specifically this is a problem for ralink rt2500-pci cards where
local->hw.queues is 2. There this causes rt2x00queue_get_tx_queue() to
return NULL and the following error to be logged: "ieee80211 phy0:
rt2x00mac_tx: Error - Attempt to send packet over invalid queue 2",
after which association with the AP fails.

Other callers of __ieee80211_select_queue() skip calling it when
local->hw.queues < IEEE80211_NUM_ACS, add the same check to
ieee80211_tx_control_port(). This fixes ralink rt2500-pci and
similar cards when less then 4 tx-queues no longer working.

Fixes: 10cb8e617560 ("mac80211: enable QoS support for nl80211 ctrl port")
Cc: Markus Theil <markus.theil@tu-ilmenau.de>
Suggested-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 net/mac80211/tx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index bf7fe6cd9dfc..13249e97a069 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -5878,6 +5878,9 @@ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 	skb_reset_network_header(skb);
 	skb_reset_mac_header(skb);
 
+	if (local->hw.queues < IEEE80211_NUM_ACS)
+		goto start_xmit;
+
 	/* update QoS header to prioritize control port frames if possible,
 	 * priorization also happens for control port frames send over
 	 * AF_PACKET
@@ -5905,6 +5908,7 @@ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 	}
 	rcu_read_unlock();
 
+start_xmit:
 	/* mutex lock is only needed for incrementing the cookie counter */
 	mutex_lock(&local->mtx);
 
-- 
2.37.3