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   1 From e44de90453bb2b46a523df78c39eb896bab35dcd Mon Sep 17 00:00:00 2001
   2 From: Govindaraj Saminathan <quic_gsaminat@quicinc.com>
   3 Date: Tue, 29 Nov 2022 13:04:02 +0200
   4 Subject: [PATCH] wifi: ath11k: Fix race condition with struct
   5  htt_ppdu_stats_info
   6
   7 A crash happens when running the traffic with multiple clients:
   8
   9 Crash Signature : Unable to handle kernel paging request at
  10 virtual address ffffffd700970918 During the crash, PC points to
  11 "ieee80211_tx_rate_update+0x30/0x68 [mac80211]"
  12 LR points to "ath11k_dp_htt_htc_t2h_msg_handler+0x5a8/0x8a0 [ath11k]".
  13
  14 Struct ppdu_stats_info is allocated and accessed from event callback via copy
  15 engine tasklet, this has a problem when freeing it from ath11k_mac_op_stop().
  16
  17 Use data_lock during entire ath11k_dp_htt_get_ppdu_desc() call to protect
  18 struct htt_ppdu_stats_info access and to avoid race condition when accessing it
  19 from ath11k_mac_op_stop().
  20
  21 Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.7.0.1-01744-QCAHKSWPL_SILICONZ-1
  22
  23 Signed-off-by: Govindaraj Saminathan <quic_gsaminat@quicinc.com>
  24 Co-developed-by: Karthikeyan Kathirvel <quic_kathirve@quicinc.com>
  25 Signed-off-by: Karthikeyan Kathirvel <quic_kathirve@quicinc.com>
  26 Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
  27 Link: https://lore.kernel.org/r/20221124071104.22506-1-quic_kathirve@quicinc.com
  28 ---
  29  drivers/net/wireless/ath/ath11k/dp_rx.c | 22 +++++++++++-----------
  30  1 file changed, 11 insertions(+), 11 deletions(-)
  31
  32 --- a/drivers/net/wireless/ath/ath11k/dp_rx.c
  33 +++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
  34 @@ -1535,13 +1535,12 @@ struct htt_ppdu_stats_info *ath11k_dp_ht
  35  {
  36         struct htt_ppdu_stats_info *ppdu_info;
  37
  38 -       spin_lock_bh(&ar->data_lock);
  39 +       lockdep_assert_held(&ar->data_lock);
  40 +
  41         if (!list_empty(&ar->ppdu_stats_info)) {
  42                 list_for_each_entry(ppdu_info, &ar->ppdu_stats_info, list) {
  43 -                       if (ppdu_info->ppdu_id == ppdu_id) {
  44 -                               spin_unlock_bh(&ar->data_lock);
  45 +                       if (ppdu_info->ppdu_id == ppdu_id)
  46                                 return ppdu_info;
  47 -                       }
  48                 }
  49
  50                 if (ar->ppdu_stat_list_depth > HTT_PPDU_DESC_MAX_DEPTH) {
  51 @@ -1553,16 +1552,13 @@ struct htt_ppdu_stats_info *ath11k_dp_ht
  52                         kfree(ppdu_info);
  53                 }
  54         }
  55 -       spin_unlock_bh(&ar->data_lock);
  56
  57         ppdu_info = kzalloc(sizeof(*ppdu_info), GFP_ATOMIC);
  58         if (!ppdu_info)
  59                 return NULL;
  60
  61 -       spin_lock_bh(&ar->data_lock);
  62         list_add_tail(&ppdu_info->list, &ar->ppdu_stats_info);
  63         ar->ppdu_stat_list_depth++;
  64 -       spin_unlock_bh(&ar->data_lock);
  65
  66         return ppdu_info;
  67  }
  68 @@ -1586,16 +1582,17 @@ static int ath11k_htt_pull_ppdu_stats(st
  69         ar = ath11k_mac_get_ar_by_pdev_id(ab, pdev_id);
  70         if (!ar) {
  71                 ret = -EINVAL;
  72 -               goto exit;
  73 +               goto out;
  74         }
  75
  76         if (ath11k_debugfs_is_pktlog_lite_mode_enabled(ar))
  77                 trace_ath11k_htt_ppdu_stats(ar, skb->data, len);
  78
  79 +       spin_lock_bh(&ar->data_lock);
  80         ppdu_info = ath11k_dp_htt_get_ppdu_desc(ar, ppdu_id);
  81         if (!ppdu_info) {
  82                 ret = -EINVAL;
  83 -               goto exit;
  84 +               goto out_unlock_data;
  85         }
  86
  87         ppdu_info->ppdu_id = ppdu_id;
  88 @@ -1604,10 +1601,13 @@ static int ath11k_htt_pull_ppdu_stats(st
  89                                      (void *)ppdu_info);
  90         if (ret) {
  91                 ath11k_warn(ab, "Failed to parse tlv %d\n", ret);
  92 -               goto exit;
  93 +               goto out_unlock_data;
  94         }
  95
  96 -exit:
  97 +out_unlock_data:
  98 +       spin_unlock_bh(&ar->data_lock);
  99 +
 100 +out:
 101         rcu_read_unlock();
 102
 103         return ret;