iwlwifi: mvm: fix BAR seq ctrl reporting

There is a bug in FW where the sequence control may be
incorrect, and the driver overrides it with the value
of the ieee80211 header.

However, in BAR there is no sequence control in the header,
which result with arbitrary sequence.

This access to an unknown location is bad and it makes the
logs very confusing - so fix it.
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/tx.c

@@ -1480,6 +1480,7 @@ static void iwl_mvm_rx_tx_cmd_single(struct iwl_mvm *mvm,
 	while (!skb_queue_empty(&skbs)) {
 		struct sk_buff *skb = __skb_dequeue(&skbs);
 		struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+		struct ieee80211_hdr *hdr = (void *)skb->data;
 		bool flushed = false;
 
 		skb_freed++;
@@ -1524,11 +1525,11 @@ static void iwl_mvm_rx_tx_cmd_single(struct iwl_mvm *mvm,
 			info->flags |= IEEE80211_TX_STAT_AMPDU_NO_BACK;
 		info->flags &= ~IEEE80211_TX_CTL_AMPDU;
 
-		/* W/A FW bug: seq_ctl is wrong when the status isn't success */
-		if (status != TX_STATUS_SUCCESS) {
-			struct ieee80211_hdr *hdr = (void *)skb->data;
+		/* W/A FW bug: seq_ctl is wrong upon failure / BAR frame */
+		if (ieee80211_is_back_req(hdr->frame_control))
+			seq_ctl = 0;
+		else if (status != TX_STATUS_SUCCESS)
 			seq_ctl = le16_to_cpu(hdr->seq_ctrl);
-		}
 
 		if (unlikely(!seq_ctl)) {
 			struct ieee80211_hdr *hdr = (void *)skb->data;