writing to shared folder errors with 'Protocol error' when 'VBoxControl sharedfolder list' runs

[David Lesaffre]

On a Windows 7 host, using VirtualBox 4.0.10 (also happened with 4.0.8), I have an Ubuntu Lucid host running (kernel 2.6.32-28-generic), with the corresponding guest additions.

Scenario:

• define a SharedFolder, say C:\vbShare, named vbShare
• mount the share in the Ubuntu guest (automount, or mount with 'mount -t vboxsf ..', or mount with 'mount.vboxsf ..', makes no difference)
• in one xterm session, run

  # dd if=/dev/urandom of=/media/sf_vbShare/random_data.txt bs=1M count=100
  

• in another xterm session, while the above command runs, run

  # VBoxControl sharedfolder list
  

• the first command errors out with

  dd: writing '/media/sf_vbShare/rando_data.txt': Protocol error
  

I'm using 'dd' to be able to reproduce a more general problem. Copying or moving a big enough file to the shared folder results in the same error message when the 'VBoxControl sharedfolder list' command is run before the copy/move operation is finished.

The error was first observed from within a Terminal server session running in the Ubuntu guest, copying a large file to the shared folder.

The error is also reproducible with a Gentoo Linux guest (kernel 2.6.35-gentoo-r15, with outdated guest additions (3.2.12)).

When this error occurs, there is no change in the VBox.log file of the VM session.

[David Lesaffre]

VBox.log