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Commit c52873e5 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
Browse files

usb: cdc-acm: make sure a refcount is taken early enough 



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 303911cf

drivers/usb/class/cdc-acm.c

+7 −5
Original line number Diff line number Diff line
@@ -1301,10 +1301,6 @@ static int acm_probe(struct usb_interface *intf, 
	tty_port_init(&acm->port);

	acm->port.ops = &acm_port_ops;



	minor = acm_alloc_minor(acm);

	if (minor < 0)

		goto alloc_fail1;



	ctrlsize = usb_endpoint_maxp(epctrl);

	readsize = usb_endpoint_maxp(epread) *

				(quirks == SINGLE_RX_URB ? 1 : 2);
@@ -1312,6 +1308,13 @@ static int acm_probe(struct usb_interface *intf, 
	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)

		goto alloc_fail1;



	acm->minor = minor;

	acm->dev = usb_dev;

	if (h.usb_cdc_acm_descriptor)
@@ -1458,7 +1461,6 @@ static int acm_probe(struct usb_interface *intf, 
	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)) {