[PATCH 2/5] ath10k: fix WARNING: suspicious RCU usage

[Shuah Khan <skhan@linuxfoundation.org>]

ieee80211_find_sta_by_ifaddr() must be called under the RCU lock and
the resulting pointer is only valid under RCU lock as well.

Fix ath10k_wmi_tlv_parse_peer_stats_info() to hold RCU lock before it
calls ieee80211_find_sta_by_ifaddr() and release it when the resulting
pointer is no longer needed. The log below shows the problem.

While at it, fix ath10k_wmi_tlv_op_pull_peer_stats_info() to do the same.

=============================
WARNING: suspicious RCU usage
5.11.0-rc7+ #20 Tainted: G        W
-----------------------------
include/linux/rhashtable.h:594 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
               rcu_scheduler_active = 2, debug_locks = 1
no locks held by ksoftirqd/5/44.

stack backtrace:
CPU: 5 PID: 44 Comm: ksoftirqd/5 Tainted: G        W         5.11.0-rc7+ #20
Hardware name: LENOVO 10VGCTO1WW/3130, BIOS M1XKT45A 08/21/2019
Call Trace:
 dump_stack+0x7d/0x9f
 lockdep_rcu_suspicious+0xdb/0xe5
 __rhashtable_lookup+0x1eb/0x260 [mac80211]
 ieee80211_find_sta_by_ifaddr+0x5b/0xc0 [mac80211]
 ath10k_wmi_tlv_parse_peer_stats_info+0x3e/0x90 [ath10k_core]
 ath10k_wmi_tlv_iter+0x6a/0xc0 [ath10k_core]
 ? ath10k_wmi_tlv_op_pull_mgmt_tx_bundle_compl_ev+0xe0/0xe0 [ath10k_core]
 ath10k_wmi_tlv_op_rx+0x5da/0xda0 [ath10k_core]
 ? trace_hardirqs_on+0x54/0xf0
 ? ath10k_ce_completed_recv_next+0x4e/0x60 [ath10k_core]
 ath10k_wmi_process_rx+0x1d/0x40 [ath10k_core]
 ath10k_htc_rx_completion_handler+0x115/0x180 [ath10k_core]
 ath10k_pci_process_rx_cb+0x149/0x1b0 [ath10k_pci]
 ? ath10k_htc_process_trailer+0x2d0/0x2d0 [ath10k_core]
 ? ath10k_pci_sleep.part.0+0x6a/0x80 [ath10k_pci]
 ath10k_pci_htc_rx_cb+0x15/0x20 [ath10k_pci]
 ath10k_ce_per_engine_service+0x61/0x80 [ath10k_core]
 ath10k_ce_per_engine_service_any+0x7d/0xa0 [ath10k_core]
 ath10k_pci_napi_poll+0x48/0x120 [ath10k_pci]
 net_rx_action+0x136/0x500
 __do_softirq+0xc6/0x459
 ? smpboot_thread_fn+0x2b/0x1f0
 run_ksoftirqd+0x2b/0x60
 smpboot_thread_fn+0x116/0x1f0
 kthread+0x14b/0x170
 ? smpboot_register_percpu_thread+0xe0/0xe0
 ? __kthread_bind_mask+0x70/0x70
 ret_from_fork+0x22/0x30

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/net/wireless/ath/ath10k/wmi-tlv.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/wmi-tlv.c b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
index 7b5834157fe5..615157dd6866 100644
--- a/drivers/net/wireless/ath/ath10k/wmi-tlv.c
+++ b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
@@ -225,6 +225,7 @@ static int ath10k_wmi_tlv_parse_peer_stats_info(struct ath10k *ar, u16 tag, u16
 	const struct wmi_tlv_peer_stats_info *stat = ptr;
 	struct ieee80211_sta *sta;
 	struct ath10k_sta *arsta;
+	int ret = 0;
 
 	if (tag != WMI_TLV_TAG_STRUCT_PEER_STATS_INFO)
 		return -EPROTO;
@@ -240,10 +241,12 @@ static int ath10k_wmi_tlv_parse_peer_stats_info(struct ath10k *ar, u16 tag, u16
 		   __le32_to_cpu(stat->last_tx_rate_code),
 		   __le32_to_cpu(stat->last_tx_bitrate_kbps));
 
+	rcu_read_lock();
 	sta = ieee80211_find_sta_by_ifaddr(ar->hw, stat->peer_macaddr.addr, NULL);
 	if (!sta) {
 		ath10k_warn(ar, "not found station for peer stats\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto exit;
 	}
 
 	arsta = (struct ath10k_sta *)sta->drv_priv;
@@ -252,7 +255,9 @@ static int ath10k_wmi_tlv_parse_peer_stats_info(struct ath10k *ar, u16 tag, u16
 	arsta->tx_rate_code = __le32_to_cpu(stat->last_tx_rate_code);
 	arsta->tx_bitrate_kbps = __le32_to_cpu(stat->last_tx_bitrate_kbps);
 
-	return 0;
+exit:
+	rcu_read_unlock();
+	return ret;
 }
 
 static int ath10k_wmi_tlv_op_pull_peer_stats_info(struct ath10k *ar,
@@ -573,13 +578,13 @@ static void ath10k_wmi_event_tdls_peer(struct ath10k *ar, struct sk_buff *skb)
 	case WMI_TDLS_TEARDOWN_REASON_TX:
 	case WMI_TDLS_TEARDOWN_REASON_RSSI:
 	case WMI_TDLS_TEARDOWN_REASON_PTR_TIMEOUT:
+		rcu_read_lock();
 		station = ieee80211_find_sta_by_ifaddr(ar->hw,
 						       ev->peer_macaddr.addr,
 						       NULL);
 		if (!station) {
 			ath10k_warn(ar, "did not find station from tdls peer event");
-			kfree(tb);
-			return;
+			goto exit;
 		}
 		arvif = ath10k_get_arvif(ar, __le32_to_cpu(ev->vdev_id));
 		ieee80211_tdls_oper_request(
@@ -590,6 +595,8 @@ static void ath10k_wmi_event_tdls_peer(struct ath10k *ar, struct sk_buff *skb)
 					);
 		break;
 	}
+exit:
+	rcu_read_unlock();
 	kfree(tb);
 }
 
-- 
2.27.0