3.16.78-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Oliver Neukum <oneukum@xxxxxxxx>
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)")
Reported-and-tested-by: syzbot+1b2449b7b5dc240d107a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Link: https://lore.kernel.org/r/20190808142119.7998-1-oneukum@xxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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
@@ -1371,13 +1371,6 @@ made_compressed_probe:
goto alloc_fail;
}
- minor = acm_alloc_minor(acm);
- if (minor == ACM_TTY_MINORS) {
- 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);
@@ -1385,6 +1378,16 @@ 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;
@@ -1540,7 +1543,6 @@ 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)) {
