linux-kernel - [RESEND PATCH v2] Bluetooth: hci_uart: fix race during initialization

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Message-ID: <f5ea6c5c-1904-22a4-72f2-d4050878dd26@gmail.com>
Date: Sat, 1 Feb 2025 19:24:31 +0300
From: Arseniy Krasnov <oxffffaa@...il.com>
To: Marcel Holtmann <marcel@...tmann.org>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc: linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
 oxffffaa@...il.com
Subject: [RESEND PATCH v2] Bluetooth: hci_uart: fix race during initialization

'hci_register_dev()' calls power up function, which is executed by
kworker - 'hci_power_on()'. This function does access to bluetooth chip
using callbacks from 'hci_ldisc.c', for example 'hci_uart_send_frame()'.
Now 'hci_uart_send_frame()' checks 'HCI_UART_PROTO_READY' bit set, and
if not - it fails. Problem is that 'HCI_UART_PROTO_READY' is set after
'hci_register_dev()', and there is tiny chance that 'hci_power_on()' will
be executed before setting this bit. In that case HCI init logic fails.

Patch moves setting of 'HCI_UART_PROTO_READY' before calling function
'hci_uart_register_dev()'.

Signed-off-by: Arseniy Krasnov <oxffffaa@...il.com>
---
 Changelog v1->v2:
 * Move 'set_bit()' before 'hci_uart_register_dev()' instead of
   adding new bit 'HCI_UART_PROTO_INIT'.

 drivers/bluetooth/hci_ldisc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 30192bb083549..07b9aa09bbe2e 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -704,12 +704,13 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)

 	hu->proto = p;

+	set_bit(HCI_UART_PROTO_READY, &hu->flags);
+
 	err = hci_uart_register_dev(hu);
 	if (err) {
 		return err;
 	}

-	set_bit(HCI_UART_PROTO_READY, &hu->flags);
 	return 0;
 }

-- 
2.30.1