ath11k: Avoid NULL ptr access during mgmt tx cleanup

Currently 'ar' reference is not added in skb_cb during
WMI mgmt tx. Though this is generally not used during tx completion
callbacks, on interface removal the remaining idr cleanup callback
uses the ar ptr from skb_cb from mgmt txmgmt_idr. Hence
fill them during tx call for proper usage.

Also free the skb which is missing currently in these
callbacks.

Crash_info:

[19282.489476] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[19282.489515] pgd = 91eb8000
[19282.496702] [00000000] *pgd=00000000
[19282.502524] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
[19282.783728] PC is at ath11k_mac_vif_txmgmt_idr_remove+0x28/0xd8 [ath11k]
[19282.789170] LR is at idr_for_each+0xa0/0xc8

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.5.0.1-00729-QCAHKSWPL_SILICONZ-3 v2
Signed-off-by: Sriram R <[email protected]>
Signed-off-by: Kalle Valo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Sriram R

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

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: BSD-3-Clause-Clear
 /*
  * Copyright (c) 2018-2019 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2021 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #include <net/mac80211.h>
@@ -5224,23 +5225,32 @@ static int __ath11k_set_antenna(struct ath11k *ar, u32 tx_ant, u32 rx_ant)
 	return 0;
 }
 
-int ath11k_mac_tx_mgmt_pending_free(int buf_id, void *skb, void *ctx)
+static void ath11k_mac_tx_mgmt_free(struct ath11k *ar, int buf_id)
 {
-	struct sk_buff *msdu = skb;
+	struct sk_buff *msdu;
 	struct ieee80211_tx_info *info;
-	struct ath11k *ar = ctx;
-	struct ath11k_base *ab = ar->ab;
 
 	spin_lock_bh(&ar->txmgmt_idr_lock);
-	idr_remove(&ar->txmgmt_idr, buf_id);
+	msdu = idr_remove(&ar->txmgmt_idr, buf_id);
 	spin_unlock_bh(&ar->txmgmt_idr_lock);
-	dma_unmap_single(ab->dev, ATH11K_SKB_CB(msdu)->paddr, msdu->len,
+
+	if (!msdu)
+		return;
+
+	dma_unmap_single(ar->ab->dev, ATH11K_SKB_CB(msdu)->paddr, msdu->len,
 			 DMA_TO_DEVICE);
 
 	info = IEEE80211_SKB_CB(msdu);
 	memset(&info->status, 0, sizeof(info->status));
 
 	ieee80211_free_txskb(ar->hw, msdu);
+}
+
+int ath11k_mac_tx_mgmt_pending_free(int buf_id, void *skb, void *ctx)
+{
+	struct ath11k *ar = ctx;
+
+	ath11k_mac_tx_mgmt_free(ar, buf_id);
 
 	return 0;
 }
@@ -5249,17 +5259,10 @@ static int ath11k_mac_vif_txmgmt_idr_remove(int buf_id, void *skb, void *ctx)
 {
 	struct ieee80211_vif *vif = ctx;
 	struct ath11k_skb_cb *skb_cb = ATH11K_SKB_CB((struct sk_buff *)skb);
-	struct sk_buff *msdu = skb;
 	struct ath11k *ar = skb_cb->ar;
-	struct ath11k_base *ab = ar->ab;
 
-	if (skb_cb->vif == vif) {
-		spin_lock_bh(&ar->txmgmt_idr_lock);
-		idr_remove(&ar->txmgmt_idr, buf_id);
-		spin_unlock_bh(&ar->txmgmt_idr_lock);
-		dma_unmap_single(ab->dev, skb_cb->paddr, msdu->len,
-				 DMA_TO_DEVICE);
-	}
+	if (skb_cb->vif == vif)
+		ath11k_mac_tx_mgmt_free(ar, buf_id);
 
 	return 0;
 }
@@ -5274,6 +5277,8 @@ static int ath11k_mac_mgmt_tx_wmi(struct ath11k *ar, struct ath11k_vif *arvif,
 	int buf_id;
 	int ret;
 
+	ATH11K_SKB_CB(skb)->ar = ar;
+
 	spin_lock_bh(&ar->txmgmt_idr_lock);
 	buf_id = idr_alloc(&ar->txmgmt_idr, skb, 0,
 			   ATH11K_TX_MGMT_NUM_PENDING_MAX, GFP_ATOMIC);