[PATCH AUTOSEL 4.19 04/12] Bluetooth: vhci: Fix race when opening vhci device

[Sasha Levin <sashal@kernel.org>]

From: Arkadiusz Bokowy <arkadiusz.bokowy@gmail.com>

[ Upstream commit 92d4abd66f7080075793970fc8f241239e58a9e7 ]

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>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/bluetooth/hci_vhci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index 22f9145a426fd..29d8b5896d6e4 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -82,7 +82,10 @@ 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;
-- 
2.42.0