ath10k: Fix suspicious RCU usage warning in ath10k_wmi_tlv_parse_peer_stats_info()

The ieee80211_find_sta_by_ifaddr call in
ath10k_wmi_tlv_parse_peer_stats_info must be called while holding the
RCU read lock. Otherwise, the following warning will be seen when RCU
usage checking is enabled:

=============================
WARNING: suspicious RCU usage
5.10.3 #8 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/1/16.

stack backtrace:
CPU: 1 PID: 16 Comm: ksoftirqd/1 Tainted: G        W         5.10.3 #8
Hardware name: HP Grunt/Grunt, BIOS Google_Grunt.11031.104.0 09/05/2019
Call Trace:
 dump_stack+0xab/0x115
 sta_info_hash_lookup+0x71/0x1e9 [mac80211]
 ? lock_is_held_type+0xe6/0x12f
 ? __kasan_kmalloc+0xfb/0x112
 ieee80211_find_sta_by_ifaddr+0x12/0x61 [mac80211]
 ath10k_wmi_tlv_parse_peer_stats_info+0xbd/0x10b [ath10k_core]
 ath10k_wmi_tlv_iter+0x8b/0x1a1 [ath10k_core]
 ? ath10k_wmi_tlv_iter+0x1a1/0x1a1 [ath10k_core]
 ath10k_wmi_tlv_event_peer_stats_info+0x103/0x13b [ath10k_core]
 ath10k_wmi_tlv_op_rx+0x722/0x80d [ath10k_core]
 ath10k_htc_rx_completion_handler+0x16e/0x1d7 [ath10k_core]
 ath10k_pci_process_rx_cb+0x116/0x22c [ath10k_pci]
 ? ath10k_htc_process_trailer+0x332/0x332 [ath10k_core]
 ? _raw_spin_unlock_irqrestore+0x34/0x61
 ? lockdep_hardirqs_on+0x8e/0x12e
 ath10k_ce_per_engine_service+0x55/0x74 [ath10k_core]
 ath10k_ce_per_engine_service_any+0x76/0x84 [ath10k_core]
 ath10k_pci_napi_poll+0x49/0x141 [ath10k_pci]
 net_rx_action+0x11a/0x347
 __do_softirq+0x2d3/0x539
 run_ksoftirqd+0x4b/0x86
 smpboot_thread_fn+0x1d0/0x2ab
 ? cpu_report_death+0x7f/0x7f
 kthread+0x189/0x191
 ? cpu_report_death+0x7f/0x7f
 ? kthread_blkcg+0x31/0x31
 ret_from_fork+0x22/0x30

Fixes: 0f7cb268 ("ath10k: add rx bitrate report for SDIO")
Signed-off-by: Anand K Mistry <amistry@google.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210202134451.1.I0d2e83c42755671b7143504b62787fd06cd914ed@changeid

drivers/net/wireless/ath/ath10k/wmi-tlv.c

@@ -240,8 +240,10 @@ 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) {
+		rcu_read_unlock();
 		ath10k_warn(ar, "not found station for peer stats\n");
 		return -EINVAL;
 	}
@@ -251,6 +253,7 @@ static int ath10k_wmi_tlv_parse_peer_stats_info(struct ath10k *ar, u16 tag, u16
 	arsta->rx_bitrate_kbps = __le32_to_cpu(stat->last_rx_bitrate_kbps);
 	arsta->tx_rate_code = __le32_to_cpu(stat->last_tx_rate_code);
 	arsta->tx_bitrate_kbps = __le32_to_cpu(stat->last_tx_bitrate_kbps);
+	rcu_read_unlock();
 
 	return 0;
 }