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wifi: mt76: mt7921: fix potential deadlock in mt7921_roc_abort_sync

PATCH New Sean Wang 1 participant 1 message Jan 26

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Arm MediaTek MediaTek MT76 wireless LAN driver
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Sean Wang

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PATCH 1/1 wifi: mt76: mt7921: fix potential deadlock in mt7921_roc_abort_sync

From: Sean Wang <[email protected]>

roc_abort_sync() can deadlock with roc_work(). roc_work() holds dev->mt76.mutex, while cancel_work_sync() waits for roc_work() to finish. If the caller already owns the same mutex, both sides block and no progress is possible.

This deadlock can occur during station removal when mt76_sta_state() -> mt76_sta_remove() -> mt7921_mac_sta_remove() -> mt7921_roc_abort_sync() invokes cancel_work_sync() while roc_work() is still running and holding dev->mt76.mutex.

This avoids the mutex deadlock and preserves exactly-once work ownership.

Fixes 352d966126e6 ("wifi: mt76: mt7921: fix a potential association failure upon resuming")
Co-developed-by Quan Zhou <[email protected]>
Signed-off-by Quan Zhou <[email protected]>
Signed-off-by Sean Wang <[email protected]>
---
 drivers/net/wireless/mediatek/mt76/mt7921/main.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)
drivers/net/wireless/mediatek/mt76/mt7921/main.c +8 -5
index 05793a786644..ddb81ca6bda0 100644
@@ -371,12 +371,15 @@ void mt7921_roc_abort_sync(struct mt792x_dev *dev)
 {
 	struct mt792x_phy *phy = &dev->phy;
 
+	if (!test_and_clear_bit(MT76_STATE_ROC, &phy->mt76->state))
+		return;
+
 	timer_delete_sync(&phy->roc_timer);
-	cancel_work_sync(&phy->roc_work);
-	if (test_and_clear_bit(MT76_STATE_ROC, &phy->mt76->state))
-		ieee80211_iterate_interfaces(mt76_hw(dev),
-					     IEEE80211_IFACE_ITER_RESUME_ALL,
-					     mt7921_roc_iter, (void *)phy);
+	cancel_work(&phy->roc_work);
+
+	ieee80211_iterate_interfaces(mt76_hw(dev),
+				     IEEE80211_IFACE_ITER_RESUME_ALL,
+				     mt7921_roc_iter, (void *)phy);
 }
 EXPORT_SYMBOL_GPL(mt7921_roc_abort_sync);
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