linux-kernel - Re: [PATCH 5.10 047/126] ath10k: hold RCU lock when calling ieee80211_find_sta_by

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Message-ID: <20210405153452.GC32232@amd>
Date:   Mon, 5 Apr 2021 17:34:52 +0200
From:   Pavel Machek <pavel@....cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 047/126] ath10k: hold RCU lock when calling
 ieee80211_find_sta_by_ifaddr()

Hi!

> Fix ath10k_wmi_tlv_op_pull_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.

It does that. But is also does the unlock even if it did not take the
lock:

> +++ b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
> @@ -576,13 +576,13 @@ 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(
> @@ -593,6 +593,9 @@ static void ath10k_wmi_event_tdls_peer(struct ath10k *ar, struct sk_buff *skb)
>  					);
>  		break;
>  	}
> +
> +exit:
> +	rcu_read_unlock();
>  	kfree(tb);
>  }

The switch only takes the lock in 3 branches, but it is released
unconditionally at the end.

Something like this?

Best regards,
								Pavel

Signed-off-by: Pavel Machek (CIP) <pavel@...x.de>

diff --git a/drivers/net/wireless/ath/ath10k/wmi-tlv.c b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
index e7072fc4f487..e03ff56d938b 100644
--- a/drivers/net/wireless/ath/ath10k/wmi-tlv.c
+++ b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
@@ -582,20 +582,19 @@ static void ath10k_wmi_event_tdls_peer(struct ath10k *ar, struct sk_buff *skb)
 						       NULL);
 		if (!station) {
 			ath10k_warn(ar, "did not find station from tdls peer event");
-			goto exit;
-		}
-		arvif = ath10k_get_arvif(ar, __le32_to_cpu(ev->vdev_id));
-		ieee80211_tdls_oper_request(
+		} else {
+			arvif = ath10k_get_arvif(ar, __le32_to_cpu(ev->vdev_id));
+			ieee80211_tdls_oper_request(
 					arvif->vif, station->addr,
 					NL80211_TDLS_TEARDOWN,
 					WLAN_REASON_TDLS_TEARDOWN_UNREACHABLE,
 					GFP_ATOMIC
 					);
+		}
+		rcu_read_unlock();
 		break;
 	}
 
-exit:
-	rcu_read_unlock();
 	kfree(tb);
 }
 


-- 
http://www.livejournal.com/~pavelmachek

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