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

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Message-ID: <95904850-fe5c-4866-3da6-3e021c6becf8@salutedevices.com>
Date: Thu, 30 Jan 2025 21:34:10 +0300
From: Arseniy Krasnov <avkrasnov@...utedevices.com>
To: Luiz Augusto von Dentz <luiz.dentz@...il.com>
CC: Marcel Holtmann <marcel@...tmann.org>, <oxffffaa@...il.com>,
	<linux-bluetooth@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel@...utedevices.com>
Subject: Re: [PATCH v2] Bluetooth: hci_uart: fix race during initialization

Hi, sorry ping

Thanks

On 08.01.2025 15:39, Arseniy Krasnov wrote:
> 
> 
> On 19.12.2024 23:07, Arseniy Krasnov wrote:
>>
>>
>> On 19.12.2024 22:18, Luiz Augusto von Dentz wrote:
>>> Hi Arseniy,
>>>
>>> On Tue, Dec 17, 2024 at 3:12 AM Arseniy Krasnov
>>> <avkrasnov@...utedevices.com> wrote:
>>>>
>>>> '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 <avkrasnov@...utedevices.com>
>>>> ---
>>>>  Changelog v1->v2:
>>>>  * Move 'set_bit()' before 'hci_uart_register_dev()' instead of
>>>>    adding new bit 'HCI_UART_PROTO_INIT'.
>>>
>>> What drivers/controllers this was tested with? I want to make sure
>>> this doesn't cause regressions to other drivers if there are perhaps
>>> some drivers assuming HCI_UART_PROTO_READY was set in a certain order.
>>
>> Hi,
>>
>> I tested this on:
>>
>> CONFIG_BT=y
>> CONFIG_BT_HCIUART=y
>> CONFIG_BT_HCIUART_H4=y
> 
> Hi, sorry, but is this enough info about my test env ?
> 
> Thanks
> 
>>
>> Yes, my v1 patchset with extra INIT bit was targeted to keep
>> original behaviour - e.g. PROTO_READY bit usage still the same,
>> just adding extra bit to handle this specific case.
>>
>> Thanks
>>
>>>
>>>>  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
>>>
>>>
>>>