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From:   Arkadiusz Bokowy <arkadiusz.bokowy@gmail.com>
To:     linux-bluetooth@vger.kernel.org
Cc:     Arkadiusz Bokowy <arkadiusz.bokowy@gmail.com>
Subject: [PATCH] Bluetooth: vhci: Fix race when opening vhci device
Date:   Wed, 20 Sep 2023 17:30:07 +0200
Message-Id: <20230920153008.967330-1-arkadiusz.bokowy@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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When the vhci device is opened in the two-step way, i.e.: open device
then write a vendor packet with requested controller type, the device
shall respond with a vendor packet which includes HCI index of created
interface.

When the virtual HCI is created, the host sends a reset request to the
controller. This request is processed by the vhci_send_frame() function.
However, this request is send by a different thread, so it might happen
that this HCI request will be received before the vendor response is
queued in the read queue. This results in the HCI vendor response and
HCI reset request inversion in the read queue which leads to improper
behavior of btvirt:

> dmesg
[1754256.640122] Bluetooth: MGMT ver 1.22
[1754263.023806] Bluetooth: MGMT ver 1.22
[1754265.043775] Bluetooth: hci1: Opcode 0x c03 failed: -110

In order to synchronize vhci two-step open/setup process with virtual
HCI initialization, this patch adds internal lock when queuing data in
the vhci_send_frame() function.

Signed-off-by: Arkadiusz Bokowy <arkadiusz.bokowy@gmail.com>
---
 drivers/bluetooth/hci_vhci.c | 3 +++
 net/bluetooth/hci_sync.c     | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index 40e2b9fa11a2..f3892e9ce800 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -74,7 +74,10 @@ static int vhci_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
 	struct vhci_data *data = hci_get_drvdata(hdev);
 
 	memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1);
+
+	mutex_lock(&data->open_mutex);
 	skb_queue_tail(&data->readq, skb);
+	mutex_unlock(&data->open_mutex);
 
 	wake_up_interruptible(&data->read_wait);
 	return 0;
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 3640d73f9595..2a7d432436a2 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -152,7 +152,7 @@ struct sk_buff *__hci_cmd_sync_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
 	struct sk_buff *skb;
 	int err = 0;
 
-	bt_dev_dbg(hdev, "Opcode 0x%4x", opcode);
+	bt_dev_dbg(hdev, "Opcode 0x%4.4x", opcode);
 
 	hci_req_init(&req, hdev);
 
@@ -248,7 +248,7 @@ int __hci_cmd_sync_status_sk(struct hci_dev *hdev, u16 opcode, u32 plen,
 	skb = __hci_cmd_sync_sk(hdev, opcode, plen, param, event, timeout, sk);
 	if (IS_ERR(skb)) {
 		if (!event)
-			bt_dev_err(hdev, "Opcode 0x%4x failed: %ld", opcode,
+			bt_dev_err(hdev, "Opcode 0x%4.4x failed: %ld", opcode,
 				   PTR_ERR(skb));
 		return PTR_ERR(skb);
 	}
-- 
2.34.1