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Commit 8fed0075 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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usb: cdc-acm: make sure a refcount is taken early enough 



commit c52873e5a1ef72f845526d9f6a50704433f9c625 upstream.

destroy() will decrement the refcount on the interface, so that
it needs to be taken so early that it never undercounts.

Fixes: 7fb57a01 ("USB: cdc-acm: Fix potential deadlock (lockdep warning)")
Cc: stable <stable@vger.kernel.org>
Reported-and-tested-by: default avatar <syzbot+1b2449b7b5dc240d107a@syzkaller.appspotmail.com>
Signed-off-by: default avatarOliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20190808142119.7998-1-oneukum@suse.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8f67bc7c

drivers/usb/class/cdc-acm.c

+10 −8
Original line number Diff line number Diff line
@@ -1319,13 +1319,6 @@ made_compressed_probe: 
	if (acm == NULL)

		goto alloc_fail;



	minor = acm_alloc_minor(acm);

	if (minor < 0) {

		dev_err(&intf->dev, "no more free acm devices\n");

		kfree(acm);

		return -ENODEV;

	}



	ctrlsize = usb_endpoint_maxp(epctrl);

	readsize = usb_endpoint_maxp(epread) *

				(quirks == SINGLE_RX_URB ? 1 : 2);
@@ -1333,6 +1326,16 @@ made_compressed_probe: 
	acm->writesize = usb_endpoint_maxp(epwrite) * 20;

	acm->control = control_interface;

	acm->data = data_interface;



	usb_get_intf(acm->control); /* undone in destruct() */



	minor = acm_alloc_minor(acm);

	if (minor < 0) {

		dev_err(&intf->dev, "no more free acm devices\n");

		kfree(acm);

		return -ENODEV;

	}



	acm->minor = minor;

	acm->dev = usb_dev;

	acm->ctrl_caps = ac_management_function;
@@ -1474,7 +1477,6 @@ skip_countries: 
	usb_driver_claim_interface(&acm_driver, data_interface, acm);

	usb_set_intfdata(data_interface, acm);



	usb_get_intf(control_interface);

	tty_dev = tty_port_register_device(&acm->port, acm_tty_driver, minor,

			&control_interface->dev);

	if (IS_ERR(tty_dev)) {