On 17.06.2021 21:51:30, Pavel Skripkin wrote:

In ems_usb_disconnect() dev pointer, which is
netdev private data, is used after free_candev() call:

	if (dev) {
		unregister_netdev(dev->netdev);
		free_candev(dev->netdev);

		unlink_all_urbs(dev);

		usb_free_urb(dev->intr_urb);

		kfree(dev->intr_in_buffer);
		kfree(dev->tx_msg_buffer);
	}

Fix it by simply moving free_candev() at the end of
the block.

Fail log:
 BUG: KASAN: use-after-free in ems_usb_disconnect
 Read of size 8 at addr ffff88804e041008 by task kworker/1:2/2895

 CPU: 1 PID: 2895 Comm: kworker/1:2 Not tainted 5.13.0-rc5+ #164
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.4
 Workqueue: usb_hub_wq hub_event
 Call Trace:
     dump_stack (lib/dump_stack.c:122)
     print_address_description.constprop.0.cold (mm/kasan/report.c:234)
     kasan_report.cold (mm/kasan/report.c:420 mm/kasan/report.c:436)
     ems_usb_disconnect (drivers/net/can/usb/ems_usb.c:683 drivers/net/can/usb/ems_usb.c:1058)

Fixes: 702171adeed3 ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface")
Signed-off-by: Pavel Skripkin <redacted>

Applied to linux-can/testing and added stable on Cc.

Thanks,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |