linux-kernel - Re: [PATCH AUTOSEL 6.4 24/25] usb: cdc-acm: move ldisc dcd notification outside of acm's read lock

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Date:   Mon, 18 Sep 2023 12:47:41 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Dan Drown <dan-netdev@...wn.org>,
        Oliver Neukum <oneukum@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 6.4 24/25] usb: cdc-acm: move ldisc dcd
 notification outside of acm's read lock

On Mon, Sep 11, 2023 at 11:19:13AM +0200, Johan Hovold wrote:
>On Fri, Sep 08, 2023 at 08:37:12PM -0400, Sasha Levin wrote:
>> From: Dan Drown <dan-netdev@...wn.org>
>>
>> [ Upstream commit f72ae60881ff685004d7de7152517607fcd9968f ]
>>
>> dcd_change notification call moved outside of the acm->read_lock
>> to protect any future tty ldisc that calls wait_serial_change()
>>
>> Signed-off-by: Dan Drown <dan-netdev@...wn.org>
>> Acked-by: Oliver Neukum <oneukum@...e.com>
>> Link: https://lore.kernel.org/r/ZN1zV/zjPgpGlHXo@vps3.drown.org
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  drivers/usb/class/cdc-acm.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
>> index 11da5fb284d0a..ca51230f44409 100644
>> --- a/drivers/usb/class/cdc-acm.c
>> +++ b/drivers/usb/class/cdc-acm.c
>> @@ -318,6 +318,16 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
>>  		}
>>
>>  		difference = acm->ctrlin ^ newctrl;
>> +
>> +		if ((difference & USB_CDC_SERIAL_STATE_DCD) && acm->port.tty) {
>> +			struct tty_ldisc *ld = tty_ldisc_ref(acm->port.tty);
>> +			if (ld) {
>> +				if (ld->ops->dcd_change)
>> +					ld->ops->dcd_change(acm->port.tty, newctrl & USB_CDC_SERIAL_STATE_DCD);
>> +				tty_ldisc_deref(ld);
>> +			}
>> +		}
>> +
>>  		spin_lock_irqsave(&acm->read_lock, flags);
>>  		acm->ctrlin = newctrl;
>>  		acm->oldcount = acm->iocount;
>
>This is a fix for a commit in 6.6-rc1 (3b563b901eef ("usb: cdc-acm: add
>PPS support")) so a backport of it makes no sense.
>
>Please drop.

Done, thanks!

-- 
Thanks,
Sasha