patch "xhci: Fix use-after-free in xhci_free_virt_device" causes kernel crashes on 4.16.8 on unplug

patch "xhci: Fix use-after-free in xhci_free_virt_device" causes kernel crashes on 4.16.8 on unplug

[Jacob Saunders]

On Linux kernel 4.16.8 (using Arch Linux) if I eject a USB 3.0 device 
from my system (unplug or "udisksctl power-off --block-device /dev/sde), 
it freezes instantly with a null pointer error in XHCI. I've been unable 
to successfully capture a kernel log of the error (and my cameras did 
not return usable results) and the screen begins scrolling 
near-immediately with hung processors in a VT.  I have done a git 
bisection (between 4.16.7 and 4.16.7) narrowing it down to the following 
commit:

commit f5331826b0b7a5f2db56a9020ddbb8ce16acdfc0
Author: Mathias Nyman <mathias.nyman@linux.intel.com>
Date:   Thu May 3 17:30:07 2018 +0300

     xhci: Fix use-after-free in xhci_free_virt_device

     commit 44a182b9d17765514fa2b1cc911e4e65134eef93 upstream.

     KASAN found a use-after-free in xhci_free_virt_device+0x33b/0x38e
     where xhci_free_virt_device() sets slot id to 0 if udev exists:
     if (dev->udev && dev->udev->slot_id)
             dev->udev->slot_id = 0;

     dev->udev will be true even if udev is freed because dev->udev is
     not set to NULL.

     set dev->udev pointer to NULL in xhci_free_dev()

     The original patch went to stable so this fix needs to be applied
     there as well.

     Fixes: a400efe455f7 ("xhci: zero usb device slot_id member when
disabling and freeing a xhci slot")
     Cc: <stable@vger.kernel.org>
     Reported-by: Guenter Roeck <linux@roeck-us.net>
     Reviewed-by: Guenter Roeck <linux@roeck-us.net>
     Tested-by: Guenter Roeck <linux@roeck-us.net>
     Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

:040000 040000 356ecdc13bf252535bd51b8558a8173dae546f19
d28f201228652e87e51ba48f5a0ad4539cca5c29 M    drivers

Can I be CC'd on future responses to this? I am not subscribed to the list.

Jacob Saunders

Re: patch "xhci: Fix use-after-free in xhci_free_virt_device" causes kernel crashes on 4.16.8 on unplug

[Greg KH]

On Fri, May 11, 2018 at 07:15:08PM -0400, Jacob Saunders wrote:
> On Linux kernel 4.16.8 (using Arch Linux) if I eject a USB 3.0 device from
> my system (unplug or "udisksctl power-off --block-device /dev/sde), it
> freezes instantly with a null pointer error in XHCI. I've been unable to
> successfully capture a kernel log of the error (and my cameras did not
> return usable results) and the screen begins scrolling near-immediately with
> hung processors in a VT.� I have done a git bisection (between 4.16.7 and
> 4.16.7) narrowing it down to the following commit:

As discussed on the linux-usb mailing list, there's a fix for this
coming.

thanks,

greg k-h