wifi: ath11k: Fix race condition with struct htt_ppdu_stats_info

A crash happens when running the traffic with multiple clients:

Crash Signature : Unable to handle kernel paging request at
virtual address ffffffd700970918 During the crash, PC points to
"ieee80211_tx_rate_update+0x30/0x68 [mac80211]"
LR points to "ath11k_dp_htt_htc_t2h_msg_handler+0x5a8/0x8a0 [ath11k]".

Struct ppdu_stats_info is allocated and accessed from event callback via copy
engine tasklet, this has a problem when freeing it from ath11k_mac_op_stop().

Use data_lock during entire ath11k_dp_htt_get_ppdu_desc() call to protect
struct htt_ppdu_stats_info access and to avoid race condition when accessing it
from ath11k_mac_op_stop().

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.7.0.1-01744-QCAHKSWPL_SILICONZ-1
Signed-off-by: Govindaraj Saminathan <quic_gsaminat@quicinc.com>
Co-developed-by: Karthikeyan Kathirvel <quic_kathirve@quicinc.com>
Signed-off-by: Karthikeyan Kathirvel <quic_kathirve@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20221124071104.22506-1-quic_kathirve@quicinc.com

drivers/net/wireless/ath/ath11k/dp_rx.c

@@ -1535,13 +1535,12 @@ struct htt_ppdu_stats_info *ath11k_dp_htt_get_ppdu_desc(struct ath11k *ar,
 {
 	struct htt_ppdu_stats_info *ppdu_info;
 
-	spin_lock_bh(&ar->data_lock);
+	lockdep_assert_held(&ar->data_lock);
+
 	if (!list_empty(&ar->ppdu_stats_info)) {
 		list_for_each_entry(ppdu_info, &ar->ppdu_stats_info, list) {
-			if (ppdu_info->ppdu_id == ppdu_id) {
-				spin_unlock_bh(&ar->data_lock);
+			if (ppdu_info->ppdu_id == ppdu_id)
 				return ppdu_info;
-			}
 		}
 
 		if (ar->ppdu_stat_list_depth > HTT_PPDU_DESC_MAX_DEPTH) {
@@ -1553,16 +1552,13 @@ struct htt_ppdu_stats_info *ath11k_dp_htt_get_ppdu_desc(struct ath11k *ar,
 			kfree(ppdu_info);
 		}
 	}
-	spin_unlock_bh(&ar->data_lock);
 
 	ppdu_info = kzalloc(sizeof(*ppdu_info), GFP_ATOMIC);
 	if (!ppdu_info)
 		return NULL;
 
-	spin_lock_bh(&ar->data_lock);
 	list_add_tail(&ppdu_info->list, &ar->ppdu_stats_info);
 	ar->ppdu_stat_list_depth++;
-	spin_unlock_bh(&ar->data_lock);
 
 	return ppdu_info;
 }
@@ -1586,16 +1582,17 @@ static int ath11k_htt_pull_ppdu_stats(struct ath11k_base *ab,
 	ar = ath11k_mac_get_ar_by_pdev_id(ab, pdev_id);
 	if (!ar) {
 		ret = -EINVAL;
-		goto exit;
+		goto out;
 	}
 
 	if (ath11k_debugfs_is_pktlog_lite_mode_enabled(ar))
 		trace_ath11k_htt_ppdu_stats(ar, skb->data, len);
 
+	spin_lock_bh(&ar->data_lock);
 	ppdu_info = ath11k_dp_htt_get_ppdu_desc(ar, ppdu_id);
 	if (!ppdu_info) {
 		ret = -EINVAL;
-		goto exit;
+		goto out_unlock_data;
 	}
 
 	ppdu_info->ppdu_id = ppdu_id;
@@ -1604,10 +1601,13 @@ static int ath11k_htt_pull_ppdu_stats(struct ath11k_base *ab,
 				     (void *)ppdu_info);
 	if (ret) {
 		ath11k_warn(ab, "Failed to parse tlv %d\n", ret);
-		goto exit;
+		goto out_unlock_data;
 	}
 
-exit:
+out_unlock_data:
+	spin_unlock_bh(&ar->data_lock);
+
+out:
 	rcu_read_unlock();
 
 	return ret;