ath10k: fix potential null dereference bugs

Smatch warns about a number of cases in ath10k where a pointer is
null-checked after it has already been dereferenced, in code involving
ath10k private virtual interface pointers.

Fix these by making the dereference happen later.

Addresses the following smatch warnings:

drivers/net/wireless/ath/ath10k/mac.c:3651 ath10k_mac_txq_init() warn: variable dereferenced before check 'txq' (see line 3649)
drivers/net/wireless/ath/ath10k/mac.c:3664 ath10k_mac_txq_unref() warn: variable dereferenced before check 'txq' (see line 3659)
drivers/net/wireless/ath/ath10k/htt_tx.c:70 __ath10k_htt_tx_txq_recalc() warn: variable dereferenced before check 'txq->sta' (see line 52)
drivers/net/wireless/ath/ath10k/htt_tx.c:740 ath10k_htt_tx_get_vdev_id() warn: variable dereferenced before check 'cb->vif' (see line 736)
drivers/net/wireless/ath/ath10k/txrx.c:86 ath10k_txrx_tx_unref() warn: variable dereferenced before check 'txq' (see line 84)
drivers/net/wireless/ath/ath10k/wmi.c:1837 ath10k_wmi_op_gen_mgmt_tx() warn: variable dereferenced before check 'cb->vif' (see line 1825)

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath10k/htt_tx.c

@@ -49,7 +49,7 @@ static void __ath10k_htt_tx_txq_recalc(struct ieee80211_hw *hw,
 				       struct ieee80211_txq *txq)
 {
 	struct ath10k *ar = hw->priv;
-	struct ath10k_sta *arsta = (void *)txq->sta->drv_priv;
+	struct ath10k_sta *arsta;
 	struct ath10k_vif *arvif = (void *)txq->vif->drv_priv;
 	unsigned long frame_cnt;
 	unsigned long byte_cnt;
@@ -67,10 +67,12 @@ static void __ath10k_htt_tx_txq_recalc(struct ieee80211_hw *hw,
 	if (ar->htt.tx_q_state.mode != HTT_TX_MODE_SWITCH_PUSH_PULL)
 		return;
 
-	if (txq->sta)
+	if (txq->sta) {
+		arsta = (void *)txq->sta->drv_priv;
 		peer_id = arsta->peer_id;
-	else
+	} else {
 		peer_id = arvif->peer_id;
+	}
 
 	tid = txq->tid;
 	bit = BIT(peer_id % 32);
@@ -733,16 +735,18 @@ static u8 ath10k_htt_tx_get_vdev_id(struct ath10k *ar, struct sk_buff *skb)
 {
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	struct ath10k_skb_cb *cb = ATH10K_SKB_CB(skb);
-	struct ath10k_vif *arvif = (void *)cb->vif->drv_priv;
+	struct ath10k_vif *arvif;
 
-	if (info->flags & IEEE80211_TX_CTL_TX_OFFCHAN)
+	if (info->flags & IEEE80211_TX_CTL_TX_OFFCHAN) {
 		return ar->scan.vdev_id;
-	else if (cb->vif)
+	} else if (cb->vif) {
+		arvif = (void *)cb->vif->drv_priv;
 		return arvif->vdev_id;
-	else if (ar->monitor_started)
+	} else if (ar->monitor_started) {
 		return ar->monitor_vdev_id;
-	else
+	} else {
 		return 0;
+	}
 }
 
 static u8 ath10k_htt_tx_get_tid(struct sk_buff *skb, bool is_eth)

drivers/net/wireless/ath/ath10k/mac.c

@@ -3675,17 +3675,18 @@ void ath10k_mgmt_over_wmi_tx_work(struct work_struct *work)
 
 static void ath10k_mac_txq_init(struct ieee80211_txq *txq)
 {
-	struct ath10k_txq *artxq = (void *)txq->drv_priv;
+	struct ath10k_txq *artxq;
 
 	if (!txq)
 		return;
 
+	artxq = (void *)txq->drv_priv;
 	INIT_LIST_HEAD(&artxq->list);
 }
 
 static void ath10k_mac_txq_unref(struct ath10k *ar, struct ieee80211_txq *txq)
 {
-	struct ath10k_txq *artxq = (void *)txq->drv_priv;
+	struct ath10k_txq *artxq;
 	struct ath10k_skb_cb *cb;
 	struct sk_buff *msdu;
 	int msdu_id;
@@ -3693,6 +3694,7 @@ static void ath10k_mac_txq_unref(struct ath10k *ar, struct ieee80211_txq *txq)
 	if (!txq)
 		return;
 
+	artxq = (void *)txq->drv_priv;
 	spin_lock_bh(&ar->txqs_lock);
 	if (!list_empty(&artxq->list))
 		list_del_init(&artxq->list);

drivers/net/wireless/ath/ath10k/txrx.c

@@ -81,10 +81,11 @@ int ath10k_txrx_tx_unref(struct ath10k_htt *htt,
 
 	skb_cb = ATH10K_SKB_CB(msdu);
 	txq = skb_cb->txq;
-	artxq = (void *)txq->drv_priv;
 
-	if (txq)
+	if (txq) {
+		artxq = (void *)txq->drv_priv;
 		artxq->num_fw_queued--;
+	}
 
 	ath10k_htt_tx_free_msdu_id(htt, tx_done->msdu_id);
 	ath10k_htt_tx_dec_pending(htt);

drivers/net/wireless/ath/ath10k/wmi.c

@@ -1826,7 +1826,7 @@ static struct sk_buff *
 ath10k_wmi_op_gen_mgmt_tx(struct ath10k *ar, struct sk_buff *msdu)
 {
 	struct ath10k_skb_cb *cb = ATH10K_SKB_CB(msdu);
-	struct ath10k_vif *arvif = (void *)cb->vif->drv_priv;
+	struct ath10k_vif *arvif;
 	struct wmi_mgmt_tx_cmd *cmd;
 	struct ieee80211_hdr *hdr;
 	struct sk_buff *skb;
@@ -1838,10 +1838,12 @@ ath10k_wmi_op_gen_mgmt_tx(struct ath10k *ar, struct sk_buff *msdu)
 	hdr = (struct ieee80211_hdr *)msdu->data;
 	fc = le16_to_cpu(hdr->frame_control);
 
-	if (cb->vif)
+	if (cb->vif) {
+		arvif = (void *)cb->vif->drv_priv;
 		vdev_id = arvif->vdev_id;
-	else
+	} else {
 		vdev_id = 0;
+	}
 
 	if (WARN_ON_ONCE(!ieee80211_is_mgmt(hdr->frame_control)))
 		return ERR_PTR(-EINVAL);