linux-kernel - Re: [PATCH 7/7] USB: cdc-acm: always claim data interface

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Date:   Mon, 22 Mar 2021 11:46:47 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] USB: cdc-acm: always claim data interface

Am Donnerstag, den 18.03.2021, 16:52 +0100 schrieb Johan Hovold:
> Make sure to always claim the data interface and bail out if it's
> already bound to another driver or isn't authorised.

Hi,

Thanks for the fixes. All previous ones are good work.
this one is problematic I am afraid.


acm_probe() has a test for the availability of the interface:

	if (!combined_interfaces && usb_interface_claimed(data_interface)) {
		/* valid in this context */
		dev_dbg(&intf->dev, "The data interface isn't available\n");
		return -EBUSY;
	}

That check is ancient. BKL still existed. If you want to remove it
and do proper error handling, that would be good. But if you do
error handling, the check has to go, too.

	Regards
		Oliver