linux-kernel - Re: [PATCH AUTOSEL 5.10 15/15] Bluetooth: hci

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Message-ID: <aAKFz3wsy+HOMphC@duo.ucw.cz>
Date: Fri, 18 Apr 2025 19:03:11 +0200
From: Pavel Machek <pavel@...x.de>
To: Sasha Levin <sashal@...nel.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Arseniy Krasnov <avkrasnov@...utedevices.com>,
	Luiz Augusto von Dentz <luiz.von.dentz@...el.com>,
	marcel@...tmann.org, luiz.dentz@...il.com,
	linux-bluetooth@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.10 15/15] Bluetooth: hci_uart: fix race during
 initialization

Hi!

> From: Arseniy Krasnov <avkrasnov@...utedevices.com>
> 
> [ Upstream commit 366ceff495f902182d42b6f41525c2474caf3f9a ]
> 
> '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()'.

Ok, but do we need to adjust the error handling?

> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -706,12 +706,13 @@ 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;
>  }

Should we clear the bit in the error path to undo the effects?

Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,        Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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