From: Oliver Neukum oneukum@suse.com
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: 7fb57a019f94e ("USB: cdc-acm: Fix potential deadlock (lockdep warning)") Cc: stable stable@vger.kernel.org Reported-and-tested-by: syzbot+1b2449b7b5dc240d107a@syzkaller.appspotmail.com Signed-off-by: Oliver Neukum oneukum@suse.com Link: https://lore.kernel.org/r/20190808142119.7998-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/usb/class/cdc-acm.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)
--- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -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)) {