[PATCH for-4.4.y 03/10] mwifiex: Fix NULL pointer dereference in skb_dequeue()

[Amit Pundir <amit.pundir@xxxxxxxxxx>]

From: Amitkumar Karwar <akarwar@xxxxxxxxxxx>

commit c44c040300d7afd79294710313a4989683e2afb1 upstream.

At couple of places in cleanup path, we are just going through the
skb queue and freeing them without unlinking. This leads to a crash
when other thread tries to do skb_dequeue() and use already freed node.

The problem is freed by unlinking skb before freeing it.

Signed-off-by: Amitkumar Karwar <akarwar@xxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>

[AmitP: Refactored to fix driver file path in linux-4.4.y]
Signed-off-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
---
 drivers/net/wireless/mwifiex/cfg80211.c |  4 +++-
 drivers/net/wireless/mwifiex/wmm.c      | 12 +++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mwifiex/cfg80211.c b/drivers/net/wireless/mwifiex/cfg80211.c
index 9a8982f581c5..6fcaa949b14a 100644
--- a/drivers/net/wireless/mwifiex/cfg80211.c
+++ b/drivers/net/wireless/mwifiex/cfg80211.c
@@ -2839,8 +2839,10 @@ int mwifiex_del_virtual_intf(struct wiphy *wiphy, struct wireless_dev *wdev)
 
 	mwifiex_stop_net_dev_queue(priv->netdev, adapter);
 
-	skb_queue_walk_safe(&priv->bypass_txq, skb, tmp)
+	skb_queue_walk_safe(&priv->bypass_txq, skb, tmp) {
+		skb_unlink(skb, &priv->bypass_txq);
 		mwifiex_write_data_complete(priv->adapter, skb, 0, -1);
+	}
 
 	if (netif_carrier_ok(priv->netdev))
 		netif_carrier_off(priv->netdev);
diff --git a/drivers/net/wireless/mwifiex/wmm.c b/drivers/net/wireless/mwifiex/wmm.c
index acccd6734e3b..ed8b69d1d65c 100644
--- a/drivers/net/wireless/mwifiex/wmm.c
+++ b/drivers/net/wireless/mwifiex/wmm.c
@@ -501,8 +501,10 @@ mwifiex_wmm_del_pkts_in_ralist_node(struct mwifiex_private *priv,
 	struct mwifiex_adapter *adapter = priv->adapter;
 	struct sk_buff *skb, *tmp;
 
-	skb_queue_walk_safe(&ra_list->skb_head, skb, tmp)
+	skb_queue_walk_safe(&ra_list->skb_head, skb, tmp) {
+		skb_unlink(skb, &ra_list->skb_head);
 		mwifiex_write_data_complete(adapter, skb, 0, -1);
+	}
 }
 
 /*
@@ -598,11 +600,15 @@ mwifiex_clean_txrx(struct mwifiex_private *priv)
 		priv->adapter->if_ops.clean_pcie_ring(priv->adapter);
 	spin_unlock_irqrestore(&priv->wmm.ra_list_spinlock, flags);
 
-	skb_queue_walk_safe(&priv->tdls_txq, skb, tmp)
+	skb_queue_walk_safe(&priv->tdls_txq, skb, tmp) {
+		skb_unlink(skb, &priv->tdls_txq);
 		mwifiex_write_data_complete(priv->adapter, skb, 0, -1);
+	}
 
-	skb_queue_walk_safe(&priv->bypass_txq, skb, tmp)
+	skb_queue_walk_safe(&priv->bypass_txq, skb, tmp) {
+		skb_unlink(skb, &priv->bypass_txq);
 		mwifiex_write_data_complete(priv->adapter, skb, 0, -1);
+	}
 	atomic_set(&priv->adapter->bypass_tx_pending, 0);
 
 	idr_for_each(&priv->ack_status_frames, mwifiex_free_ack_frame, NULL);
-- 
2.7.4