Comment 56 for bug 787091

Please download this file and extract it using
   tar zxf openeperm_kprobe.tar.gz

Then you'll need to install a few prerequisites:

  apt-get install make gcc linux-headers-2.6.32-32-generic

Enter the extracted directory and compile the kprobe:

  cd openeperm_kprobe
  make

This will compile a kprobe (kernel probe) which, while installed, will give more information on the credentials of any process which receives -EPERM or -EACCES trying to open a file. So the way to use it is, load the module, start the virtual machine which tries to use the printer, unload the module once it has failed (i.e. you see the messages about failing to open /sys/bus/usb/001/004), then unload the module and look through the logs for any meaningful information.

Load the module using: insmod openeperm.ko
Unload it using: rmmod openeperm

You can see the error messages using the command 'dmesg', and they will look like:

[ 148.939971] sys_open returned: -13
[ 148.939982] Call by: euid 1000 cap_eff 0