mac80211: backport upstream fix for unitialized lock usage

Backports upstream fix from 5.19

lockdep complains use of uninitialized spinlock at ieee80211_do_stop() [1],
for commit f856373e2f31ffd3 ("wifi: mac80211: do not wake queues on a vif
that is being stopped") guards clear_bit() using fq.lock even before
fq_init() from ieee80211_txq_setup_flows() initializes this spinlock.

According to discussion [2], Toke was not happy with expanding usage of
fq.lock. Since __ieee80211_wake_txqs() is called under RCU read lock, we
can instead use synchronize_rcu() for flushing ieee80211_wake_txqs().

Signed-off-by: Koen Vandeputte <[email protected]>

package/kernel/mac80211/patches/subsys/340-wifi-mac80211-do-not-abuse-fq.lock-in-ieee80211_do_s.patch

@@ -0,0 +1,46 @@
+From aa40d5a43526cca9439a2b45fcfdcd016594dece Mon Sep 17 00:00:00 2001
+From: Tetsuo Handa <[email protected]>
+Date: Sun, 17 Jul 2022 21:21:52 +0900
+Subject: [PATCH] wifi: mac80211: do not abuse fq.lock in ieee80211_do_stop()
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+lockdep complains use of uninitialized spinlock at ieee80211_do_stop() [1],
+for commit f856373e2f31ffd3 ("wifi: mac80211: do not wake queues on a vif
+that is being stopped") guards clear_bit() using fq.lock even before
+fq_init() from ieee80211_txq_setup_flows() initializes this spinlock.
+
+According to discussion [2], Toke was not happy with expanding usage of
+fq.lock. Since __ieee80211_wake_txqs() is called under RCU read lock, we
+can instead use synchronize_rcu() for flushing ieee80211_wake_txqs().
+
+Link: https://syzkaller.appspot.com/bug?extid=eceab52db7c4b961e9d6 [1]
+Link: https://lkml.kernel.org/r/[email protected] [2]
+Reported-by: syzbot <[email protected]>
+Signed-off-by: Tetsuo Handa <[email protected]>
+Fixes: f856373e2f31ffd3 ("wifi: mac80211: do not wake queues on a vif that is being stopped")
+Tested-by: syzbot <[email protected]>
+Acked-by: Toke Høiland-Jørgensen <[email protected]>
+Signed-off-by: Kalle Valo <[email protected]>
+Link: https://lore.kernel.org/r/[email protected]
+[ pick up commit 3598cb6e1862 ("wifi: mac80211: do not abuse fq.lock in ieee80211_do_stop()") from -next]
+Link: https://lore.kernel.org/all/[email protected]/
+Signed-off-by: Jakub Kicinski <[email protected]>
+---
+ net/mac80211/iface.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+--- a/net/mac80211/iface.c
++++ b/net/mac80211/iface.c
+@@ -377,9 +377,8 @@ static void ieee80211_do_stop(struct iee
+ 	bool cancel_scan;
+ 	struct cfg80211_nan_func *func;
+ 
+-	spin_lock_bh(&local->fq.lock);
+ 	clear_bit(SDATA_STATE_RUNNING, &sdata->state);
+-	spin_unlock_bh(&local->fq.lock);
++	synchronize_rcu(); /* flush _ieee80211_wake_txqs() */
+ 
+ 	cancel_scan = rcu_access_pointer(local->scan_sdata) == sdata;
+ 	if (cancel_scan)