Re: [edk2-devel] OVMF/QEMU shell based unit tests and writing to a virtual disk

["Laszlo Ersek" <lersek@redhat.com>]

On 10/27/20 14:26, Laszlo Ersek wrote:

> Now, another option (on Linux anyway) is to loop-mount a "raw" virtual
> disk image. This is not recommended, as it directly exposes the host
> kernel's filesystem driver(s) to metadata produced by the guest. It
> could trigger security issues in the host kernel.
> 
> (This is exactly what guestfish avoids, by running a separate Linux
> guest -- called the "libguestfs appliance" -- on top of the virtual disk
> image. The guestfish command interpreter on the host side exchanges
> commands and data with the appliance over virtio-serial. If the metadata
> on the disk image is malicious, it will break / exploit the *guest*
> kernel in the appliance. The host-side component, the guestfish command
> interpreter, only has to sanity-check the virtio-serial exchanges.)

If you trust your guest 100%, you *might* try the following:

- use a disk image file with "format=vhdx" on the QEMU command line,

- when QEMU is not running, I think you might be able to "loop-mount"
the VHDX file directly, on Windows.

Mutual exclusion remains just as important, of course.

... A reference about vhdx support:
<https://www.qemu.org/docs/master/system/images.html#cmdoption-image-formats-arg-vhdx>.

... A reference about the pitfalls with vvfat:
<https://www.qemu.org/docs/master/system/images.html#virtual-fat-disk-images>.

Thanks,
Laszlo