netdev - [PATCH] net: bluetooth: hci_core: Fix Suspicious RCU usage warnings

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Date:   Tue, 25 Feb 2020 18:38:09 +0530
From:   madhuparnabhowmik10@...il.com
To:     marcel@...tmann.org, johan.hedberg@...il.com, davem@...emloft.net,
        kuba@...nel.org
Cc:     linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, joel@...lfernandes.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        frextrite@...il.com, paulmck@...nel.org,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Subject: [PATCH] net: bluetooth: hci_core: Fix Suspicious RCU usage warnings

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

The following functions in hci_core are always called with
hdev->lock held. No need to use list_for_each_entry_rcu(), therefore
change the usage of list_for_each_entry_rcu() in these functions
to list_for_each_entry().

hci_link_keys_clear()
hci_smp_ltks_clear()
hci_smp_irks_clear()
hci_blocked_keys_clear()

Warning encountered with CONFIG_PROVE_RCU_LIST:

[   72.213184] =============================
[   72.213188] WARNING: suspicious RCU usage
[   72.213192] 5.6.0-rc1+ #5 Not tainted
[   72.213195] -----------------------------
[   72.213198] net/bluetooth/hci_core.c:2288 RCU-list traversed in non-reader section!!

[   72.213676] =============================
[   72.213679] WARNING: suspicious RCU usage
[   72.213683] 5.6.0-rc1+ #5 Not tainted
[   72.213685] -----------------------------
[   72.213689] net/bluetooth/hci_core.c:2298 RCU-list traversed in non-reader section!!

[   72.214195] =============================
[   72.214198] WARNING: suspicious RCU usage
[   72.214201] 5.6.0-rc1+ #5 Not tainted
[   72.214204] -----------------------------
[   72.214208] net/bluetooth/hci_core.c:2308 RCU-list traversed in non-reader section!!

[  333.456972] =============================
[  333.456979] WARNING: suspicious RCU usage
[  333.457001] 5.6.0-rc1+ #5 Not tainted
[  333.457007] -----------------------------
[  333.457014] net/bluetooth/hci_core.c:2318 RCU-list traversed in non-reader section!!

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 net/bluetooth/hci_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index cbbc34a006d1..8ddd1bea02be 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -2285,7 +2285,7 @@ void hci_link_keys_clear(struct hci_dev *hdev)
 {
 	struct link_key *key;
 
-	list_for_each_entry_rcu(key, &hdev->link_keys, list) {
+	list_for_each_entry(key, &hdev->link_keys, list) {
 		list_del_rcu(&key->list);
 		kfree_rcu(key, rcu);
 	}
@@ -2295,7 +2295,7 @@ void hci_smp_ltks_clear(struct hci_dev *hdev)
 {
 	struct smp_ltk *k;
 
-	list_for_each_entry_rcu(k, &hdev->long_term_keys, list) {
+	list_for_each_entry(k, &hdev->long_term_keys, list) {
 		list_del_rcu(&k->list);
 		kfree_rcu(k, rcu);
 	}
@@ -2305,7 +2305,7 @@ void hci_smp_irks_clear(struct hci_dev *hdev)
 {
 	struct smp_irk *k;
 
-	list_for_each_entry_rcu(k, &hdev->identity_resolving_keys, list) {
+	list_for_each_entry(k, &hdev->identity_resolving_keys, list) {
 		list_del_rcu(&k->list);
 		kfree_rcu(k, rcu);
 	}
@@ -2315,7 +2315,7 @@ void hci_blocked_keys_clear(struct hci_dev *hdev)
 {
 	struct blocked_key *b;
 
-	list_for_each_entry_rcu(b, &hdev->blocked_keys, list) {
+	list_for_each_entry(b, &hdev->blocked_keys, list) {
 		list_del_rcu(&b->list);
 		kfree_rcu(b, rcu);
 	}
-- 
2.17.1