Re: [PATCH] net: can: fix use-after-free in ems_usb_disconnect

Marc Kleine-Budde
2021-06-18T07:17:30Z

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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 <paskripkin@gmail.com>

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

Thanks,
Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
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