wil6210: fix race condition between BACK event and Rx data

While handling Rx packet, BACK event arrives and frees tid_ampdu_rx array.
This causes kernel panic while accessing already freed spinlock

The fix is to remove tid_ampdu_rx[]'s spinlock and instead use single
sta's spinlock to guard the whole tid_ampdu_rx array.

Signed-off-by: Dedy Lansky <qca_dlansky@qca.qualcomm.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/wil6210/main.c b/drivers/net/wireless/ath/wil6210/main.c
index 22e9b8a..d2f2c1e 100644
--- a/drivers/net/wireless/ath/wil6210/main.c
+++ b/drivers/net/wireless/ath/wil6210/main.c
@@ -95,9 +95,16 @@
 	}
 
 	for (i = 0; i < WIL_STA_TID_NUM; i++) {
-		struct wil_tid_ampdu_rx *r = sta->tid_rx[i];
+		struct wil_tid_ampdu_rx *r;
+		unsigned long flags;
+
+		spin_lock_irqsave(&sta->tid_rx_lock, flags);
+
+		r = sta->tid_rx[i];
 		sta->tid_rx[i] = NULL;
 		wil_tid_ampdu_rx_free(wil, r);
+
+		spin_unlock_irqrestore(&sta->tid_rx_lock, flags);
 	}
 	for (i = 0; i < ARRAY_SIZE(wil->vring_tx); i++) {
 		if (wil->vring2cid_tid[i][0] == cid)
@@ -267,9 +274,13 @@
 
 int wil_priv_init(struct wil6210_priv *wil)
 {
+	uint i;
+
 	wil_dbg_misc(wil, "%s()\n", __func__);
 
 	memset(wil->sta, 0, sizeof(wil->sta));
+	for (i = 0; i < WIL6210_MAX_CID; i++)
+		spin_lock_init(&wil->sta[i].tid_rx_lock);
 
 	mutex_init(&wil->mutex);
 	mutex_init(&wil->wmi_mutex);