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From:   Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To:     marcel@holtmann.org, johan.hedberg@gmail.com, luiz.dentz@gmail.com,
        davem@davemloft.net, kuba@kernel.org, matthieu.baerts@tessares.net,
        stefan@datenfreihafen.org
Cc:     Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
        linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, skhan@linuxfoundation.org,
        gregkh@linuxfoundation.org,
        linux-kernel-mentees@lists.linuxfoundation.org
Subject: [PATCH v3 2/2] Bluetooth: fix inconsistent lock state in rfcomm_connect_ind
Date:   Wed, 21 Jul 2021 17:38:32 +0800
Message-Id: <20210721093832.78081-3-desmondcheongzx@gmail.com>
In-Reply-To: <20210721093832.78081-1-desmondcheongzx@gmail.com>
References: <20210721093832.78081-1-desmondcheongzx@gmail.com>
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Commit fad003b6c8e3d ("Bluetooth: Fix inconsistent lock state with
RFCOMM") fixed a lockdep warning due to sk->sk_lock.slock being
acquired without disabling softirq while the lock is also used in
softirq context. This was done by disabling interrupts before calling
bh_lock_sock in rfcomm_sk_state_change.

Later, this was changed in commit e6da0edc24ee ("Bluetooth: Acquire
sk_lock.slock without disabling interrupts") to disable softirqs
only.

However, there is another instance of sk->sk_lock.slock being acquired
without disabling softirq in rfcomm_connect_ind. This patch fixes this
by disabling local bh before the call to bh_lock_sock.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
---
 net/bluetooth/rfcomm/sock.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index ae6f80730561..d8734abb2df4 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -974,6 +974,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc *
 	if (!parent)
 		return 0;
 
+	local_bh_disable();
 	bh_lock_sock(parent);
 
 	/* Check for backlog size */
@@ -1002,6 +1003,7 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel, struct rfcomm_dlc *
 
 done:
 	bh_unlock_sock(parent);
+	local_bh_enable();
 
 	if (test_bit(BT_SK_DEFER_SETUP, &bt_sk(parent)->flags))
 		parent->sk_state_change(parent);
-- 
2.25.1