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From:   Wen Gong <quic_wgong@quicinc.com>
To:     <johannes@sipsolutions.net>, <ath11k@lists.infradead.org>
CC:     <linux-wireless@vger.kernel.org>, <wgong@codeaurora.org>
Subject: [PATCH] wifi: mac80211: allow transmitting EAPOL frames with tainted key
Date:   Tue, 1 Aug 2023 02:47:51 -0400
Message-ID: <20230801064751.25803-1-quic_wgong@quicinc.com>
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Lower layer device driver stop/wake TX by calling ieee80211_stop_queue()/
ieee80211_wake_queue() while hw scan. Sometimes hw scan and PTK rekey are
running in parallel, when M4 sent from wpa_supplicant arrive while the TX
queue is stopped, then the M4 will pending send, and then new key install
from wpa_supplicant. After TX queue wake up by lower layer device driver,
the M4 will be dropped by below call stack.

When key install started, the current key flag is set KEY_FLAG_TAINTED in
ieee80211_pairwise_rekey(), and then mac80211 wait key install complete by
lower layer device driver. Meanwhile ieee80211_tx_h_select_key() will return
TX_DROP for the M4 in step 12 below, and then ieee80211_free_txskb() called
by ieee80211_tx_dequeue(), so the M4 will not send and free, then the rekey
process failed becaue AP not receive M4. Please see details in steps below.

There are a interval between KEY_FLAG_TAINTED set for current key flag and
install key complete by lower layer device driver, the KEY_FLAG_TAINTED is
set in this interval, all packet including M4 will be dropped in this
interval, the interval is step 8~13 as below.

issue steps:
      TX thread                 install key thread
1.   stop_queue                      -idle-
2.   sending M4                      -idle-
3.   M4 pending                      -idle-
4.     -idle-                  starting install key from wpa_supplicant
5.     -idle-                  =>ieee80211_key_replace()
6.     -idle-                  =>ieee80211_pairwise_rekey() and set
                                 currently key->flags |= KEY_FLAG_TAINTED
7.     -idle-                  =>ieee80211_key_enable_hw_accel()
8.     -idle-                  =>drv_set_key() and waiting key install
                                 complete from lower layer device driver
9.   wake_queue                     -waiting state-
10.  re-sending M4                  -waiting state-
11.  =>ieee80211_tx_h_select_key()  -waiting state-
12.  drop M4 by KEY_FLAG_TAINTED    -waiting state-
13.    -idle-                   install key complete with success/fail
                                  success: clear flag KEY_FLAG_TAINTED
                                  fail: start disconnect

Hence add check in step 11 above to allow the EAPOL send out in the
interval. If lower layer device driver use the old key/cipher to encrypt
the M4, then AP received/decrypt M4 correctly, after M4 send out, lower
layer device driver install the new key/cipher to hardware and return
success.

If lower layer device driver use new key/cipher to send the M4, then AP
will/should drop the M4, then it is same result with this issue, AP will/
should kick out station as well as this issue.

issue log:
kworker/u16:4-5238  [000]  6456.108926: stop_queue:           phy1 queue:0, reason:0
wpa_supplicant-961  [003]  6456.119737: rdev_tx_control_port: wiphy_name=phy1 name=wlan0 ifindex=6 dest=ARRAY[9e, 05, 31, 20, 9b, d0] proto=36488 unencrypted=0
wpa_supplicant-961  [003]  6456.119839: rdev_return_int_cookie: phy1, returned 0, cookie: 504
wpa_supplicant-961  [003]  6456.120287: rdev_add_key:         phy1, netdev:wlan0(6), key_index: 0, mode: 0, pairwise: true, mac addr: 9e:05:31:20:9b:d0
wpa_supplicant-961  [003]  6456.120453: drv_set_key:          phy1 vif:wlan0(2) sta:9e:05:31:20:9b:d0 cipher:0xfac04, flags=0x9, keyidx=0, hw_key_idx=0
kworker/u16:9-3829  [001]  6456.168240: wake_queue:           phy1 queue:0, reason:0
kworker/u16:9-3829  [001]  6456.168255: drv_wake_tx_queue:    phy1 vif:wlan0(2) sta:9e:05:31:20:9b:d0 ac:0 tid:7
kworker/u16:9-3829  [001]  6456.168305: cfg80211_control_port_tx_status: wdev(1), cookie: 504, ack: false
wpa_supplicant-961  [003]  6459.167982: drv_return_int:       phy1 - -110

issue call stack:
nl80211_frame_tx_status+0x230/0x340 [cfg80211]
cfg80211_control_port_tx_status+0x1c/0x28 [cfg80211]
ieee80211_report_used_skb+0x374/0x3e8 [mac80211]
ieee80211_free_txskb+0x24/0x40 [mac80211]
ieee80211_tx_dequeue+0x644/0x954 [mac80211]
ath10k_mac_tx_push_txq+0xac/0x238 [ath10k_core]
ath10k_mac_op_wake_tx_queue+0xac/0xe0 [ath10k_core]
drv_wake_tx_queue+0x80/0x168 [mac80211]
__ieee80211_wake_txqs+0xe8/0x1c8 [mac80211]
_ieee80211_wake_txqs+0xb4/0x120 [mac80211]
ieee80211_wake_txqs+0x48/0x80 [mac80211]
tasklet_action_common+0xa8/0x254
tasklet_action+0x2c/0x38
__do_softirq+0xdc/0x384

Signed-off-by: Wen Gong <quic_wgong@quicinc.com>
---
 net/mac80211/tx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index d8460a14b6bd..c003d9826c9b 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -664,7 +664,8 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
 		}
 
 		if (unlikely(tx->key && tx->key->flags & KEY_FLAG_TAINTED &&
-			     !ieee80211_is_deauth(hdr->frame_control)))
+			     !ieee80211_is_deauth(hdr->frame_control)) &&
+			     tx->skb->protocol != tx->sdata->control_port_protocol)
 			return TX_DROP;
 
 		if (!skip_hw && tx->key &&

base-commit: b21fe5be53eb873c02e7479372726c8aeed171e3
-- 
2.40.1